PHA compositions comprising PBS and PBSA and methods for their production

ABSTRACT

Compositions of PHAs with PBS and PBSA are described and methods of making the same.

RELATED APPLICATION

This application is the U.S. National Stage of International ApplicationNo.: PCT/US2010/040037, filed on Jun. 25, 2010, which designates theU.S., published in English, and claims the benefit of U.S. ProvisionalApplication No. 61/269,582, filed on Jun. 26, 2009. The entire teachingsof the above applications are incorporated herein by reference.

BACKGROUND

Biodegradable plastics are of increasing industrial interest asreplacements or supplements for non-biodegradable plastics in a widerange of applications and in particular for packaging applications. Oneclass of biodegradable polymers is the polyhydroxyalkanoates (PHAs),which are linear, aliphatic polyesters that can be produced by numerousmicroorganisms for use as intracellular storage material. Articles madefrom the polymers are generally recognized by soil microbes as a foodsource. There has therefore been a great deal of interest in thecommercial development of these polymers, particularly for disposableconsumer items. The polymers exhibit good biodegradability and usefulphysical properties.

In some applications, the rapid biodegradability of PHAs is a problem,and therefore a need exists for compositions that assist in controllingthe rate of biodegradation of PHAs.

SUMMARY OF THE INVENTION

In accordance with embodiments of the invention, compositions ofbranched polymer compositions comprising polyhydroxyalkanoates (PHAs)and either poly(butylene succinate) (PBS) or polybutylene succinateadipate (PBSA) or combinations thereof are provided. The PHAs arereactive blended with the PBS or PBSA and in some embodiments,combinations of the polymers. In particular, when the polymers aremelt-blended in the presence of an a branching agent, for example,organic peroxide, (e.g., reactive blending or reactive melt blending)the resultant compositions display many unexpected synergies in meltrheology, melt stability, processing and properties, such as filmprocessing and film properties. In addition, the biodegradation kineticsof PHB copolymers can be slowed down by combining some PBS and/or PBSAinto the composition. In certain aspects, the process of reactiveblending further includes the use of a reactive cross-linking agentresulting in improved properties. In one embodiment, the PHA and PBS isblended, i.e., to a homogeneous blend. In another embodiment, the PHAand PBSA is blended, i.e., to a homogenous blend. In certain aspects,the polymers of the compositions are mixed together to form a blend.

In related embodiments, reacting with a branching agent is performed inthe presence of a co-agent (also referred to herein, as a “cross-linkingagent), thereby forming a branched polymer blend. The conditions of thereaction are suitable for reacting the branching agent alone or with across-linking agent and a polymer blend. A “branched” polymer is apolymer with a branching of the polymer chain or cross-linking of two ormore polymer chains.

The cross-linking agent when reacted, for example, at its epoxidegroup(s) or double bond(s), becomes bonded to another molecule, e.g., apolymer or branched polymer. As a consequence the multiple moleculesbecome cross-linked through the reactive group on the cross-linkingagent. An “epoxy functional compound” is a cross-linking agentcomprising two or more epoxy functional groups.

In accordance with other related aspects of the invention, thefunctional group of the cross-linking agent is an epoxy-functionalcompound, for example, an epoxy-functional styrene-acrylic polymer, anepoxy-functional acrylic copolymer, an epoxy-functional polyolefincopolymer, oligomers comprising glycidyl groups with epoxy functionalside chains, an epoxy-functional poly(ethylene-glycidylmethacrylate-co-methacrylate), or an epoxidized oil,poly(ethylene-co-methacrylate-coglycidyl methacrylate, ethylene-n-butylacrylate-glycidyl methacrylate or combinations thereof.

In another related embodiment, the cross-linking agent contains at leasttwo reactive double bonds. These cross-linking agents include but is notlimited to the following: diallyl phthalate, pentaerythritoltetraacrylate, trimethylolpropane triacrylate, pentaerythritoltriacrylate, dipentaerythritol pentaacrylate, diethylene glycoldimethacrylate, bis(2-methacryloxyethyl) phosphate, or combinationsthereof.

In accordance with other related embodiments, a method of preparing abranched polymer composition, comprising reacting a PHA and a PBS with abranching agent, and forming a branched polymer composition comprising abranched PHA and PBS blend is described. In another embodiment, a methodof preparing a branched polymer composition is described, comprisingreacting a PHA and PBSA with a branching agent, and forming a branchedpolymer composition comprising a branched PHA and PBSA blend. In certainembodiments, the method wherein the composition further comprises PBSA.

Additives may also be included in the compositions and methods of theinventions. In particular embodiments, a nucleating agent is added.

In still another embodiment, a method of preparing a film comprising abranched polymer composition is described. The method comprises reactinga PHA with a branching agent, reacting a PBS with a branching agent, andforming a branched PBS polymer composition. Then, exposing the branchedPHA composition to conditions that cause melting of the PHA, therebyforming a molten branched PHA composition, exposing the branch PBScomposition to conditions that cause melting of the PBS, thereby forminga molten branched PBS composition, co-extruding the molten PHAcompositions and the molten PBS compositions to form a multi-layeredfilm; thereby making a film comprising branched PHA and branched PBSlayers.

Also described is a method of preparing a film comprising a branchedpolymer composition, comprising reacting a PHA with a branching agent,thereby forming a branched PHA polymer composition, reacting a PBSA witha branching agent, thereby forming a branched PBSA polymer composition,exposing the branch PHA composition to conditions that cause melting ofthe PHA, thereby forming a molten branched PHA composition, exposing thebranch PBS composition to conditions that cause melting of the PBSA,thereby forming a molten branched PBSA composition, co-extruding themolten PHA compositions and the molten PBSA compositions to form amulti-layered film; thereby making a film comprising branched PHA andbranched PBS.

In still another embodiment, a method of making an article comprising abranched PHA and branched PBS composition comprising the steps of:melt-blending PHA and PBS and a branching agent under conditions thatcause melting and branching of the PHA polymer and the PBS, therebyforming a molten branched polymer composition; and forming an articlefrom the branched molten polymer composition; thereby making an articlecomprising branched polymer composition of branched PHA and branchedPBS.

In yet another method an article is prepared comprising a branched PHAand branched PBSA composition comprising the steps of: melt-blending PHAand PBSA and a branching agent under conditions that cause melting andbranching of the PHA polymer and the PBSA, thereby forming a moltenbranched polymer composition; and forming an article from the branchedmolten polymer composition; thereby making an article comprisingbranched polymer composition of branched PHA and branched PBSA.

In certain embodiment, a film is prepared by the methods describedherein, the resultant film has greater tear resistance according to ASTMD1922-06, greater puncture resistance according to D1709-04, or greatertensile strength according to D882-02 than a corresponding PHA film madewithout PBS and/or PBSA. In some aspects, the film possesses propertiesthat are 25% greater, 50% greater or 75-100% greater. In certainaspects, the film is a blend of branched PHA and branched PBS orbranched PHA and branched PBSA. In other aspects, the film compriseslayers of branched PHA alternating with branched PBS or branched PBSA.

In accordance with another related aspects, compositions are describedthat comprise branched PHA and branched PBS or branched PHA and branchedPBSA. In particular embodiments, the PHA is a PHA blend of about 58-62%homo-polymer of 3-hydroxybutanoic acid, and about 38-42% copolymer of3-hydroxybutanoic acid and 4-hydroxybutanoic acid, where the4-hydroxybutanoic acid is about 8-14% weight percent or a PHBV with thehydroxyvalerate is about 7% weight percent or a blend of a copolymer ofabout 34-38% homo-polymer of 3-hydroxybutanoic acid, and about 22-26%co-polymer of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid, wherethe 4-hydroxybutanoic acid is approximately 8-14 weight percent, and acopolymer of about 38-42% co-polymer of 3-hydroxybutanoic acid and4-hydroxybutanoic acid with the 4-hydroxybutanoic acid composition beingnominally 25-33 weight percent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot showing apparent Viscosity vs. time.

FIG. 2 is a plot showing G′ of vs. Wt % PBS.

FIG. 3 is a plot showing capillary stability vs. Wt % PBS.

FIG. 4 is a plot showing G′ of vs. Wt % PBSA.

FIG. 5 is a plot showing capillary stability vs. Wt % PBSA.

FIG. 6 is a plot of formulations vs. controls.

FIG. 7 is a plot showing G′ of vs. Wt % PBS in Blend.

FIG. 8 is a plot showing capillary stability vs. Wt % PBS in Blend.

FIG. 9 is a photo demonstrating different percentage of the blend ininjection molded test bars.

FIG. 10 is a plot showing weight loss of the 12 different formulationsof Table 10.

FIG. 11 is a plot showing weight loss of the 8 different formulations ofTable 13.

DETAILED DESCRIPTION

This invention relates to compositions comprising polyhydroxyalkanoates(PHAs) and poly(butylene succinate) (PBS) and/or poly (butylenesuccinate adipate) (PBSA) reacted with branching agents, methods ofmaking the compositions, and articles made from the compositions. Thecompositions are useful in applications such as articles, includingfilm, injection molded articles, sheets, foam and thermoformed articles,the like.

The invention provides branched polymer compositions and methods ofpreparing branched polymers with improved mechanical and rheologicalproperties. The polymer compositions include preparing branched PHA andbranched PBS or branched PBSA compositions and combinations of thesepolymers.

Combining (e.g., mixing or blending) the polymer blends in the presenceof peroxide provides the following benefits compared to combining thepolymer blends without any reactive chemistry: (1) higher melt strength,(2) improved melt stability and/or better melt capillary stability,resulting in a broader processing window for the overall composition,(3) synergistic film properties, e.g., film tear properties of thecompositions are better than PHA or PBS and/or PBSA film by itself, (4)higher toughness for injection molded bars, and (5) lower flash duringinjection molding process.

The use of cross-linking agents (co-agents) further improve the desiredproperties of the polymer composition over the starting compositionswithout the cross-linking agents and branching agents. In one aspect,the cross-linking agents comprise two or more reactive groups such asdouble bonds or epoxides. These cross-linking agents react with andbecome covalently bonded (connected) to the polymer. The connection ofmultiple chains through these cross-linking agents form a branchedpolymer. The branched polymer has increased melt strength over the meltstrength of the starting polymer.

Increased melt strength is useful in that it allows the polymers to beformed under a broader temperature range when the polymer is processed.This property for broader processing temperatures for polymerapplications, such as in the production of blown film (i.e., inpreventing or reducing bubble collapse), or cast film extrusion,thermoformed articles (i.e., preventing or reducing sheet sag duringthermoforming), profile extruded articles (i.e., preventing or reducingsag), non-woven fibers, monofilament, etc.

The polymers' stability is effected at processing temperatures and canaccordingly experience a drop in melt strength. This can causedifficulties in processing these polymers. These shortcomings areaddressed by the compositions and methods of the invention.Additionally, the improvement shown in films made from the methods arecompositions described herein are greater tensile strength, tearresistance and greater puncture resistance.

The methods and branched compositions of the invention improve the meltstrength of polymer compositions, a desirable property for many polymerproduct applications. Melt strength is a rheological property that canbe measured a number of ways. One measure is G.′ G′ is the polymerstorage modulus measured at melt processing temperatures.

Physical properties and rheological properties of polymeric materialsdepend on the molecular weight and distribution of the polymer.“Molecular weight” is calculated in a number of different ways. Unlessother wise indicated, “molecular weight” refers to weight averagemolecular weight.

“Number average molecular weight” (M_(n)) represents the arithmetic meanof the distribution, and is the sum of the products of the molecularweights of each fraction, multiplied by its mole fraction(ΣN_(i)M_(i)/ΣN_(i)M_(i)).

“Weight average molecular weight” (M_(w)) is the sum of the products ofthe molecular weight of each fraction, multiplied by its weight fraction(ΣN_(i)M_(i) ²/ΣN_(i)M_(i)). M_(w) is generally greater than or equal toM_(n).

One way of increasing the melt strength is by branching the polymers(PHA, PBS and PBSA and combinations thereof), and various methods foraccomplishing this are described herein. Branching of PHA is a result ofreacting with branching agents, for example, peroxides. Also,cross-linking agents, for example, reactive compounds (compounds withepoxy groups and compounds with reactive double bonds) that enhance orincrease the branching of the polymer, can also be used.

Addition of other reactive polymeric compounds, such as reactiveacrylics, can also be employed to the rate of branching architecture ofthe PHA. The use and selection of additives to these compositions resultin improved properties. All of these methods are described herein.

Polybutylene Succinate and Poly Butylene Succinate Adipate

Poly butylene succinate (PBS) and poly butylene succinate adipate (PBSA)are synthetic, petroleum-based aliphatic polyesters, made bycondensation polymerization followed by chain extension usingmulti-functional isocyanates. PBS is a combination of 1,4 butane dioland succinic acid, while PBSA is a combination of 1,4 butane diol,succinic acid, and adipic acid. Although usually synthesized frompetroleum, it is also possible for the monomers that make up PBS andPBSA to be produced from biobased feedstock.

PBS and PBSA are commercially available for example from, ShowaHighPolymer, Japan; SkyGreen BDP, Korea; and SK Polymer, Ire ChemicalsCo., Korea; and Sqehan Co, Korea; among others.

The two polymers are reportedly biodegradable at ambient temperatures(i.e., are “cold compostable”) in soil and marine conditions. PBSdegrades more slowly compared to PBSA. PBS is hydro-biodegradable andbegins to biodegrade via a hydrolysis mechanism. Hydrolysis occurs atthe ester linkages and this results in a lowering of the polymer'smolecular weight, allowing for further degradation by micro-organisms.Further, PBS and PBSA are known to biodegrade more slowly than PHAs,which are also cold-compostable.

Of the two, PBS has higher crystallinity, and is better suited formolding, while PBSA has lower crystallinity, is better suited to filmapplications. Both polymers have a low (sub-zero) glass transitiontemperature (Tg), and their processing temperatures overlap with PHAs.As disclosed herein, PHA polymers can be combined with PBS and/or PBSAusing conventional melt-blending techniques. In this invention, theabove-mentioned blends are melt-blended in the presence of a reactiveentity such as organic peroxide branching agents; branching co-agentsmay also be used. The reactive blending approach produces compositionsthat have considerably better melt and solid-state properties comparedto the non-reactive blends. In particular, the reactive (inventive)blends have higher melt strength, broader processing window, and bettermechanical properties. As shown herein, the crystallization of PHA isinfluenced significantly by the presence of even small amounts of PBSand/or PBSA. Reactive blends were found to process very well, withimproved anti-blocking behavior, higher line speeds and betterroll-release behavior. Addition of PBS and/or PBSA to PHAs improved thetear, puncture, and tensile strength performance of PHA films. Ingeneral, PBSA performed better when blended with PHA than did PBS.Reactive blending resulted in considerably better performancecharacteristics of the finished film relative to equivalent dry blends.Addition of as little as 25% PBSA doubled the tear and punctureresistance of PHA films. The addition of PBS and PBSA also reduced flashin injection molding applications.

Polyhydroxyalkanoates (PHAS)

Polyhydroxyalkanoates are biological polyesters synthesized by a broadrange of natural and genetically engineered bacteria as well asgenetically engineered plant crops (Braunegg et al., (1998), J.Biotechnology 65:127-161; Madison and Huisman, 1999, Microbiology andMolecular Biology Reviews, 63:21-53; Poirier, 2002, Progress in LipidResearch 41:131-155). These polymers are biodegradable thermoplasticmaterials, produced from renewable resources, with the potential for usein a broad range of industrial applications (Williams & Peoples,CHEMTECH 26:38-44 (1996)). Useful microbial strains for producing PHAs,include Alcaligenes eutrophus (renamed as Ralstonia eutropha),Alcaligenes latus, Azotobacter, Aeromonas, Comamonas, Pseudomonads, andgenetically engineered organisms including genetically engineeredmicrobes such as Pseudomonas, Ralstonia and Escherichia coli.

In general, a PHA is formed by enzymatic polymerization of one or moremonomer units inside a living cell. Over 100 different types of monomershave been incorporated into the PHA polymers (Steinbüchel and Valentin,1995, FEMS Microbiol. Lett. 128:219-228. Examples of monomer unitsincorporated in PHAs include 2-hydroxybutyrate, lactic acid, glycolicacid, 3-hydroxybutyrate (hereinafter referred to as 3HB),3-hydroxypropionate (hereinafter referred to as 3HP), 3-hydroxyvalerate(hereinafter referred to as 3HV), 3-hydroxyhexanoate (hereinafterreferred to as 3HH), 3-hydroxyheptanoate (hereinafter referred to as3HHep), 3-hydroxyoctanoate (hereinafter referred to as 3HO),3-hydroxynonanoate (hereinafter referred to as 3HN), 3-hydroxydecanoate(hereinafter referred to as 3HD), 3-hydroxydodecanoate (hereinafterreferred to as 3HDd), 4-hydroxybutyrate (hereinafter referred to as4HB), 4-hydroxyvalerate (hereinafter referred to as 4HV),5-hydroxyvalerate (hereinafter referred to as 5HV), and6-hydroxyhexanoate (hereinafter referred to as 6HH). 3-hydroxyacidmonomers incorporated into PHAs are the (D) or (R) 3-hydroxyacid isomerwith the exception of 3HP which does not have a chiral center.

In some embodiments, the PHA in the methods described herein is ahomopolymer (where all monomer units are the same). Examples of PHAhomopolymers include poly 3-hydroxyalkanoates (e.g., poly3-hydroxypropionate (hereinafter referred to as P3HP), poly3-hydroxybutyrate (hereinafter referred to as PHB) and poly3-hydroxyvalerate), poly 4-hydroxyalkanoates (e.g., poly4-hydroxybutyrate (hereinafter referred to as P4HB), or poly4-hydroxyvalerate (hereinafter referred to as P4HV)) and poly5-hydroxyalkanoates (e.g., poly 5-hydroxyvalerate (hereinafter referredto as P5HV)).

In certain embodiments, the starting PHA can be a copolymer (containingtwo or more different monomer units) in which the different monomers arerandomly distributed in the polymer chain. Examples of PHA copolymersinclude poly 3-hydroxybutyrate-co-3-hydroxypropionate (hereinafterreferred to as PHB3HP), poly 3-hydroxybutyrate-co-4-hydroxybutyrate(hereinafter referred to as PHB4HB), poly3-hydroxybutyrate-co-4-hydroxyvalerate (hereinafter referred to asPHB4HV), poly 3-hydroxybutyrate-co-3-hydroxyvalerate (hereinafterreferred to as PHB3HV), poly 3-hydroxybutyrate-co-3-hydroxyhexanoate(hereinafter referred to as PHB3HH) and poly3-hydroxybutyrate-co-5-hydroxyvalerate (hereinafter referred to asPHB5HV).

By selecting the monomer types and controlling the ratios of the monomerunits in a given PHA copolymer a wide range of material properties canbe achieved. Although examples of PHA copolymers having two differentmonomer units have been provided, the PHA can have more than twodifferent monomer units (e.g., three different monomer units, fourdifferent monomer units, five different monomer units, six differentmonomer units) An example of a PHA having 4 different monomer unitswould be PHB-co-3HH-co-3HO-co-3HD or PHB-co-3-HO-co-3HD-co-3HDd (thesetypes of PHA copolymers are hereinafter referred to as PHB3HX).Typically where the PHB3HX has 3 or more monomer units the 3HB monomeris at least 70% by weight of the total monomers, preferably 85% byweight of the total monomers, most preferably greater than 90% by weightof the total monomers for example 92%, 93%, 94%, 95%, 96% by weight ofthe copolymer and the HX comprises one or more monomers selected from3HH, 3HO, 3HD, 3HDd.

The homopolymer (where all monomer units are identical) PHB and3-hydroxybutyrate copolymers (PHB3HP, PHB4HB, PHB3HV, PHB4HV, PHB5HV,PHB3HHP, hereinafter referred to as PHB copolymers) containing3-hydroxybutyrate and at least one other monomer are of particularinterest for commercial production and applications. It is useful todescribe these copolymers by reference to their material properties asfollows. Type 1 PHB copolymers typically have a glass transitiontemperature (Tg) in the range of 6° C. to −10° C., and a meltingtemperature T_(M) of between 80° C. to 180° C. Type 2 PHB copolymerstypically have a Tg of −20° C. to −50° C. and Tm of 55° C. to 90° C. Inparticular embodiments, the Type 2 copolymer has a phase component witha T_(g) of −15° C. to −45° C. and no Tm.

Preferred Type 1 PHB copolymers have two monomer units have a majorityof their monomer units being 3-hydroxybutyrate monomer by weight in thecopolymer, for example, greater than 78% 3-hydroxybutyrate monomer.Preferred PHB copolymers for this invention are biologically producedfrom renewable resources and are selected from the following group ofPHB copolymers:

-   -   PHB3HV is a Type 1 PHB copolymer where the 3HV content is in the        range of 3% to 22% by weight of the polymer and preferably in        the range of 4% to 15% by weight of the copolymer for example:        4% 3HV; 5% 3HV; 6% 3HV; 7% 3HV; 8% 3HV; 9% 3HV; 10% 3HV; 11%        3HV; 12% 3HV; 13% 3HV; 14% 3HV; 15% 3HV;    -   PHB3HP is a Type 1 PHB copolymer where the 3HP content is in the        range of 3% to 15% by weight of the copolymer and preferably in        the range of 4% to 15% by weight of the copolymer for example:        4% 3HP; 5% 3HP; 6% 3HP; 7% 3HP; 8% 3HP; 9% 3HP; 10% 3HP; 11%        3HP; 12% 3HP. 13% 3HP; 14% HIP; 15% 3HP.    -   PHB4HB is a Type 1 PHB copolymer where the 4HB content is in the        range of 3% to 15% by weight of the copolymer and preferably in        the range of 4% to 15% by weight of the copolymer for example:        4% 4HB; 5% 4HB; 6% 4HB; 7% 4HB; 8% 4HB; 9% 4HB; 10% 4HB; 11%        4HB; 12% 4HB; 13% 4HB; 14% 4HB; 15% 4HB.    -   PHB4HV is a Type 1 PHB copolymer where the 4HV content is in the        range of 3% to 15% by weight of the copolymer and preferably in        the range of 4% to 15% by weight of the copolymer for example:        4% 4HV; 5% 4HV; 6% 4HV; 7% 4HV; 8% 4HV; 9% 4HV; 10% 4HV; 11%        4HV; 12% 4HV; 13% 4HV; 14% 4HV; 15% 4HV.    -   PHB5HV is a Type 1 PHB copolymer where the 51-1V content is in        the range of 3% to 15% by weight of the copolymer and preferably        in the range of 4% to 15% by weight of the copolymer for        example: 4% 5HV; 5% 5HV; 6% 51-1V; 7% 5HV; 8% 5HV; 9% 5HV; 10%        5HV; 11% 5HV; 12% 5HV; 13% 5HV; 14% 5HV; 15% SHY.    -   PHB3HH is a Type 1 PHB copolymer where the 3HH content is in the        range of 3% to 15% by weight of the copolymer and preferably in        the range of 4% to 15% by weight of the copolymer for example:        4% 3HH; 5% 3HH; 6% 3HH; 7% 3HH; 8% 3HH; 9% 3HH; 10% 3HH; 11%        3HH; 12% 3HH; 13% 3HH; 14% 3HH; 15% 3HH;    -   PHB3HX is a Type 1 PHB copolymer where the 3HX content is        comprised of 2 or more monomers selected from 3HH, 3HO, 3HD and        3HDd and the 3HX content is in the range of 3% to 12% by weight        of the copolymer and preferably in the range of 4% to 10% by        weight of the copolymer for example: 4% 3HX; 5% 3HX; 6% 3HX; 7%        3HX; 8% 3HX; 9% 3HX; 10% 3HX by weight of the copolymer.    -   Type 2 PHB copolymers have a 3HB content of between 80% and 5%        by weight of the copolymer, for example 80%, 75%, 70%, 65%, 60%,        55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5% by weight        of the copolymer.    -   PHB4HB is a Type 2 PHB copolymer where the 4HB content is in the        range of 20% to 60% by weight of the copolymer and preferably in        the range of 25% to 50% by weight of the copolymer for example:        25% 4HB; 30% 4HB; 35% 4HB; 40% 4HB; 45% 4HB; 50% 4HB by weight        of the copolymer.    -   PHB5HV is a Type 2 PHB copolymer where the 5HV content is in the        range of 20% to 60% by weight of the copolymer and preferably in        the range of 25% to 50% by weight of the copolymer for example:        25% 5HV; 30% 5HV; 35% 5HV; 40% 5HV; 45% 5HV; 50% 5HV by weight        of the copolymer.    -   PHB3HH is a Type 2 PHB copolymer where the 3HH is in the range        of 35% to 95% by weight of the copolymer and preferably in the        range of 40% to 80% by weight of the copolymer for example: 40%        3HH; 45% 3HH; 50% 3HH; 55% 3HH, 60% 3HH; 65% 3HH; 70% 3HH; 75%        3HH; 80% 3HH by weight of the copolymer.    -   PHB3HX is a Type 2 PHB copolymer where the 3HX content is        comprised of 2 or more monomers selected from 3HH, 3HO, 3HD and        3HDd and the 3HX content is in the range of 30% to 95% by weight        of the copolymer and preferably in the range of 35% to 90% by        weight of the copolymer for example: 35% 3HX; 40% 3HX; 45% 3HX;        50% 3HX; 55% 3HX 60% 3HX; 65% 3HX; 70% 3HX; 75% 3HX; 80% 3HX;        85% 3HX; 90% 3HX by weight of the copolymer.

PHAs for use in the methods, compositions and pellets described in thisinvention are selected from: PHB or a Type 1 PHB copolymer; a PHA blendof PHB with a Type 1 PHB copolymer where the PHB content by weight ofPHA in the PHA blend is in the range of 5% to 95% by weight of the PHAin the PHA blend; a PHA blend of PHB with a Type 2 PHB copolymer wherethe PHB content by weight of the PHA in the PHA blend is in the range of5% to 95% by weight of the PHA in the PHA blend; a PHA blend of a Type 1PHB copolymer with a different Type 1 PHB copolymer and where thecontent of the first Type 1 PHB copolymer is in the range of 5% to 95%by weight of the PHA in the PHA blend; a PHA blend of a Type 1 PHBcopolymer with a Type 2 PHA copolymer where the content of the Type 1PHB copolymer is in the range of 30% to 95% by weight of the PHA in thePHA blend; a PHA blend of PHB with a Type 1 PHB copolymer and a Type 2PHB copolymer where the PHB content is in the range of 10% to 90% byweight of the PHA in the PHA blend, where the Type 1 PHB copolymercontent is in the range of 5% to 90% by weight of the PHA in the PHAblend and where the Type 2 PHB copolymer content is in the range of 5%to 90% by weight of the PHA in the PHA blend.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB withPHB3HP where the PHB content in the PHA blend is in the range of 5% to90% by weight of the PHA in the PHA blend and the 3HP content in thePHB3HP is in the range of 7% to 15% by weight of the PHB3HP.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB withPHB3HV where the PHB content of the PHA blend is in the range of 5% to90% by weight of the PHA in the PHA blend and the 3HV content in thePHB3HV is in the range of 4% to 22% by weight of the PHB3HV.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB withPHB4HB where the PHB content of the PHA blend is in the range of 5% to90% by weight of the PHA in the PHA blend and the 4HB content in thePHB4HB is in the range of 4% to 15% by weight of the PHB4HB.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB withPHB4HV where the PHB content of the PHA blend is in the range of 5% to90% by weight of the PHA in the PHA blend and the 4HV content in thePHB4HV is in the range of 4% to 15% by weight of the PHB4HV.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB withPHB5HV where the PHB content of the PHA blend is in the range of 5% to90% by weight of the PHA in the PHA blend and the 5HV content in thePHBSHV is in the range of 4% to 15% by weight of the PHBSHV.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB withPHB3HH where the PHB content of the PHA blend is in the range of 5% to90% by weight of the PHA in the PHA blend and the 3HH content in thePHB3HH is in the range of 4% to 15% by weight of the PHB3HH.

The PHA blend of PHB with a Type 1 PHB copolymer is a blend of PHB withPHB3HX where the PHB content of the PHA blend is in the range of 5% to90% by weight of the PHA in the PHA blend and the 3HX content in thePHB3HX is in the range of 4% to 15% by weight of the PHB3HX.

The PHA blend is a blend of a Type 1 PHB copolymer selected from thegroup PHB3HV, PHB3HP, PHB4HB, PHBV, PHV4HV, PHB5HV, PHB3HH and PHB3HXwith a second Type 1 PHB copolymer which is different from the firstType 1 PHB copolymer and is selected from the group PHB3HV, PHB3HP,PHB4HB, PHBV, PHV4HV, PHBSHV, PHB3HH and PHB3HX where the content of theFirst Type 1 PHB copolymer in the PHA blend is in the range of 10% to90% by weight of the total PHA in the blend.

The PHA blend of PHB with a Type 2 PHB copolymer is a blend of PHB withPHB4HB where the PHB content in the PHA blend is in the range of 30% to95% by weight of the PHA in the PHA blend and the 4HB content in thePHB4HB is in the range of 20% to 60% by weight of the PHB4HB.

The PHA blend of PHB with a Type 2 PHB copolymer is a blend of PHB withPHB5HV where the PHB content in the PHA blend is in the range of 30% to95% by weight of the PHA in the PHA blend and the 5HV content in thePHB5HV is in the range of 20% to 60% by weight of the PHB5HV.

The PHA blend of PHB with a Type 2 PHB copolymer is a blend of PHB withPHB3HH where the PHB content in the PHA blend is in the range of 35% to95% by weight of the PHA in the PHA blend and the 3HH content in thePHB3HH is in the range of 35% to 90% by weight of the PHB3HX.

The PHA blend of PHB with a Type 2 PHB copolymer is a blend of PHB withPHB3HX where the PHB content in the PHA blend is in the range of 30% to95% by weight of the PHA in the PHA blend and the 3HX content in thePHB3HX is in the range of 35% to 90% by weight of the PHB3HX.

The PHA blend is a blend of PHB with a Type 1 PHB copolymer and a Type 2PHB copolymer where the PHB content in the PHA blend is in the range of10% to 90% by weight of the PHA in the PHA blend, the Type 1 PHBcopolymer content of the PHA blend is in the range of 5% to 90% byweight of the PHA in the PHA blend and the Type 2 PHB copolymer contentin the PHA blend is in the range of 5% to 90% by weight of the PHA inthe PHA blend.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HVcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 3HV content in the PHB3HV is in the range of 3%to 22% by weight of the PHB3HV, and a PHBHX content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where the3HX content in the PHBHX is in the range of 35% to 90% by weight of thePHBHX.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HVcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 3HV content in the PHB3HV is in the range of 3%to 22% by weight of the PHB3HV, and a PHB4HB content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where the4HB content in the PHB4HB is in the range of 20% to 60% by weight of thePHB4HB.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HVcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 3HV content in the PHB3HV is in the range of 3%to 22% by weight of the PHB3HV, and a PHB5HV content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where the5HV content in the PHB5HV is in the range of 20% to 60% by weight of thePHB5HV.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB4HBcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 4HB content in the PHB4HB is in the range of 4%to 15% by weight of the PHB4HB, and a PHB4HB content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where the4HB content in the PHB4HB is in the range of 20% to 60% by weight of thePHB4HB.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB4HBcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 4HB content in the PHB4HB is in the range of 4%to 15% by weight of the PHB4HB, and a PHB5HV content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend and wherethe 5HV content in the PHB5HV is in the range of 30% to 90% by weight ofthe PHB5HV.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB4HBcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 4HB content in the PHB4HB is in the range of 4%to 15% by weight of the PHB4HB, and a PHB3HX content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend and wherethe 3HX content in the PHB3HX is in the range of 35% to 90% by weight ofthe PHB3HX.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHBSHVcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 4HV content in the PHB4HV is in the range of 3%to 15% by weight of the PHB4HV, and a PHBSHV content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where the5HV content in the PHBSHV is in the range of 30% to 90% by weight of thePHBSHV.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HHcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 3HH content in the PHB3HH is in the range of 3%to 15% by weight of the PHB3HH, and a PHB4HB content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where the41-1B content in the PHB4HB is in the range of 20% to 60% by weight ofthe PHB4HB.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HHcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 3HH content in the PHB3HH is in the range of 3%to 15% by weight of the PHB3HH, and a PHBSHV content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where theSHY content in the PHBSHV is in the range of 20% to 60% by weight of thePHBSHV.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HHcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 3HH content in the PHB3HH is in the range of 3%to 15% by weight of the PHB3HH, and a PHB3HX content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where the3HX content in the PHB3HX is in the range of 35% to 90% by weight of thePHB3HX.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HXcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 3HX content in the PHB3HX is in the range of 3%to 12% by weight of the PHB3HX, and a PHB3HX content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where the3HX content in the PHB3HX is in the range of 35% to 90% by weight of thePHB3HX.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HXcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 3HX content in the PHB3HX is in the range of 3%to 12% by weight of the PHB3HX, and a PHB4HB content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where the4HB content in the PHB4HB is in the range of 20% to 60% by weight of thePHB4HB.

For example a PHA blend can have a PHB content in the PHA blend in therange of 10% to 90% by weight of the PHA in the PHA blend, a PHB3HXcontent in the PHA blend in the range 5% to 90% by weight of the PHA inthe PHA blend, where the 3HX content in the PHB3HX is in the range of 3%to 12% by weight of the PHB3HX, and a PHB5HV content in the PHA blend inthe range of 5% to 90% by weight of the PHA in the PHA blend where the5HV content in the PHB5HV is in the range of 20% to 60% by weight of thePHB5HV.

The PHA blend is a blend as disclosed in U.S. Pub. App. No.2004/0220355, by Whitehouse, published Nov. 4, 2004, which isincorporated herein by reference in its entirety.

Microbial systems for producing the PHB copolymer PHBV are disclosed inU.S. Pat. No. 4,477,654 to Holmes. U.S. Pat. App. Pub. 2002/0164729, bySkraly and Sholl describes useful systems for producing the PHBcopolymer PHB4HB. Useful processes for producing the PHB copolymerPHB3HH have been described (Lee et al., 2000, Biotechnology andBioengineering 67:240-244; Park et al., 2001, Biomacromolecules2:248-254). Processes for producing the PHB copolymers PHB3HX have beendescribed by Matsusaki et al. (Biomacromolecules 2000, 1:17-22).

In determining the molecular weight techniques such as gel permeationchromatography (GPC) can be used. In the methodology, a polystyrenestandard is utilized. The PHA can have a polystyrene equivalent weightaverage molecular weight (in daltons) of at least 500, at least 10,000,or at least 50,000 and/or less than 2,000,000, less than 1,000,000, lessthan 1,500,000, and less than 800,000. In certain embodiments,preferably, the PHAs generally have a weight-average molecular weight inthe range of 100,000 to 700,000. For example, the molecular weight rangefor PHB and Type 1 PHB copolymers for use in this application are in therange of 400,000 daltons to 1.5 million daltons as determined by GPCmethod and the molecular weight range for Type 2 PHB copolymers for usein the application 100,000 to 1.5 million daltons.

In certain embodiments, the PHA can have a linear equivalent weightaverage molecular weight of from about 150,000 Daltons to about 500,000Daltons and a polydispersity index of from about 2.5 to about 8.0. Asused herein, weight average molecular weight and linear equivalentweight average molecular weight are determined by gel permeationchromatography, using, e.g., chloroform as both the eluent and diluentfor the PHA samples. Calibration curves for determining molecularweights are generated using linear polystyrenes as molecular weightstandards and a ‘log MW vs elution volume’ calibration method.

Blends of PHA with PBS or PBSA and Combinations Thereof

In certain embodiments, the polymers for use in the methods andcompositions are blended in the presence of additives, branching agentsand cross-linking agents to form compositions with improved properties.The percentages of PHA to PBS or PBSA are 5% to 95% by weight. Incertain compositions of the invention, the percentage of PHA to PBS orPBSA of the total polymer compositions ranges from about 95% PHA toabout 5% PBS or PBSA or about 50% PBS or PBSA to about 50% PHA. Forexample the PHA/PBS or PBSA ratio can be 95/5, 90/10, 85/15, 80/20,75/25, 70/30, 65/35, 60/40, 55/45 or 50/50.

Branched Polyhydroxyalkanoates, Branched PBS or Branched PBSA

The term “branched polymer” refers to a PHA, PBS or PBSA with branchingof the chain and/or cross-linking of two or more chains. Branching onside chains is also contemplated. Branching can be accomplished byvarious methods. Polyhydroxyalkanoate polymer described above can bebranched by branching agents by free-radical-induced cross-linking ofthe polymer. In certain embodiment, the PHA is branched prior tocombination in the method. In other embodiments, the PHA reacted withperoxide in the methods of the invention. The branching increases themelt strength of the polymer. Polyhydroxyalkanoate polymers can bebranched in any of the ways described in U.S. Pat. Nos. 6,620,869,7,208,535, 6,201,083, 6,156,852, 6,248,862, 6,201,083 and 6,096,810 allof which are incorporated herein by reference in their entirety.

The polymers of the invention can be branched according to any of themethods disclosed in WO 2010/008447 titled “Methods For Branching PHAUsing Thermolysis” or WO 2010/008445 A2 titled “Branched PHACompositions, Methods For Their Production, And Use In Applications,”both of which were filed in English on Jun. 19, 2009, and designated theUnited States. These applications are incorporated by reference hereinin their entirety.

The invention provides branched PHA copolymer blend compositions withPBS and/or PBSA that do not require the use of a compatibilizer formixing and blending that other thermoplastic polymer blend compositionsrequire. In these other compositions the compatibilizer is necessary toimprove the properties of the blends and increase the compatibility ofthe polymer composition, especially immiscible polymers.

Branching Agents

The branching agents, also referred to a free radical initiator, for usein the compositions and method described herein include organicperoxides. Peroxides are reactive molecules, and can react with polymermolecules or previously branched polymers by removing a hydrogen atomfrom the polymer backbone, leaving behind a radical. Polymer moleculeshaving such radicals on their backbone are free to combine with eachother, creating branched polymer molecules. Branching agents areselected from any suitable initiator known in the art, such asperoxides, azo-dervatives (e.g., azo-nitriles), peresters, andperoxycarbonates. Suitable peroxides for use in the present inventioninclude, but are not limited to, organic peroxides, for example dialkylorganic peroxides such as 2,5-dimethyl-2,5-di(t-butylperoxy) hexane,2,5-bis(t-butylperoxy)-2,5-dimethylhexane (available from Azko Nobel asTRIGANOX® 101), 2,5-dimethyl-di(t-butylperoxy)hexyne-3, di-t-butylperoxide, dicumyl peroxide, benzoyl peroxide, di-t-amyl peroxide,t-amylperoxy-2-ethylhexylcarbonate (TAEC), t-butyl cumyl peroxide,n-butyl-4,4-bis(t-butylperoxy)valerate,1,1-di(t-butylperoxy)-3,3,5-trimethyl-cyclohexane,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane (CPK),1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-amylperoxy)-cyclohexane,2,2-di(t-butylperoxy)butane, ethyl-3,3-di(t-butylperoxy)butyrate,2,2-di(t-amylperoxy)propane, ethyl-3,3-di(t-amylperoxy)butyrate,t-butylperoxy-acetate, t-amylperoxyacetate, t-butylperoxybenzoate,t-amylperoxybenzoate, di-t-butyldiperoxyphthalate, and the like.Combinations and mixtures of peroxides can also be used. Examples offree radical initiators include those mentioned herein, as well as thosedescribed in, e.g., Polymer Handbook, 3^(rd) Ed., J. Brandrup & E. H.Immergut, John Wiley and Sons, 1989, Ch. 2. Irradiation (e.g., e-beam orgamma irradiation) can also be used to generate PHA branching.

The efficiency of branching and crosslinking of the polymer(s) can alsobe significantly enhanced by the dispersion of organic peroxides in across-linking agent, such as a polymerizable (i.e., reactive)plasticizers. The polymerizable plasticizer should contain a reactivefunctionality, such as a reactive unsaturated double bond, whichincreases the overall branching and crosslinking efficiency.

As discussed above, when peroxides decompose, they form very high energyradicals that can extract a hydrogen atom from the polymer backbone.These radicals have short half-lives, thereby limiting the population ofbranched molecules that is produced during the active time period.

Additives

In certain embodiments, various additives are added to the compositions.Examples of these additives include antioxidants, slip/antiblock agents,pigments, UV stabilizers, fillers, plasticizers, nucleating agents,talc, wax, calcium carbonate, and radical scavengers. Additionally,polyfunctional branching agents such as divinyl benzene, triallycyanurate and the like may be added. The branching agent and/orcross-linking agent is added to one or more of these for easierincorporation into the polymer. For instance, the branching agent and/orcross-linking agent is mixed with a plasticizer, e.g., a non-reactiveplasticizer, e.g., a citric acid ester, and then compounded with thepolymer under conditions to induce branching.

Optionally, additives are included in the thermoplastic compositions ata concentration of about 0.05 to about 20% by weight of the totalcomposition. For example, the range is certain embodiments is about 0.05to about 5% of the total composition. The additive is any compound knownto those of skill in the art to be useful in the production ofthermoplastics. Exemplary additives include, e.g., plasticizers (e.g.,to increase flexibility of a thermoplastic composition), antioxidants(e.g., to protect the thermoplastic composition from degradation byozone or oxygen), ultraviolet stabilizers (e.g., to protect againstweathering), lubricants (e.g., to reduce friction), pigments (e.g., toadd color to the thermoplastic composition), flame retardants, fillers,reinforcing, mold release, and antistatic agents. It is well within theskilled practitioner's abilities to determine whether an additive shouldbe included in a thermoplastic composition and, if so, what additive andthe amount that should be added to the composition.

The additive(s) can also be prepared as a masterbatch for example, byincorporating the additive(s) in a PHA blend and producing pellets ofthe resultant composition for addition to subsequent processing. In amasterbatch the concentration of the additive(s) is (are) higher thanthe final amount for the product to allow for proportionate mixing ofthe additive in the final composition.

In poly-3-hydroxybutyrate compositions, for example, plasticizers areoften used to change the glass transition temperature and modulus of thecomposition, but surfactants may also be used. Lubricants may also beused, e.g., in injection molding applications. Plasticizers, surfactantsand lubricants may all therefore be included in the overall composition.

In other embodiments, the blend includes one or more plasticizers.Examples of plasticizers include phthalic compounds (including, but notlimited to, dimethyl phthalate, diethyl phthalate, dibutyl phthalate,dihexyl phthalate, di-n-octyl phthalate, di-2-ethylhexyl phthalate,diisooctyl phthalate, dicapryl phthalate, dinonyl phthalate, diisononylphthalate, didecyl phthalate, diundecyl phthalate, dilauryl phthalate,ditridecyl phthalate, dibenzyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate, octyl decyl phthalate, butyl octyl phthalate, octylbenzyl phthalate, n-hexyl n-decyl phthalate, n-octyl phthalate, andn-decyl phthalate), phosphoric compounds (including, but not limited to,tricresyl phosphate, trioctyl phosphate, triphenyl phosphate, octyldiphenyl phosphate, cresyl diphenyl phosphate, and trichloroethylphosphate), adipic compounds (including, but not limited to,dibutoxyethoxyethyl adipate (DBEEA), dioctyl adipate, diisooctyladipate, di-n-octyl adipate, didecyl adipate, diisodecyl adipate,n-octyl n-decyl adipate, n-heptyl adipate, and n-nonyl adipate), sebaciccompounds (including, but not limited to, dibutyl sebacate, dioctylsebacate, diisooctyl sebacate, and butyl benzyl sebacate), azelaiccompounds, citric compounds (including, but not limited to, triethylcitrate, acetyl triethyl citrate, tributyl citrate, acetyl tributylcitrate, and acetyl trioctyl citrate), glycolic compounds (including,but not limited to, methyl phthalyl ethyl glycolate, ethyl phthalylethyl glycolate, and butyl phthalyl ethyl glycolate), trimelliticcompounds (including, but not limited to, trioctyl trimellitate andtri-n-octyl n-decyl trimellitate), phthalic isomer compounds (including,but not limited to, dioctyl isophthalate and dioctyl terephthalate),ricinoleic compounds (including, but not limited to, methyl acetyl,recinoleate and butyl acetyl recinoleate), polyester compounds(including, but not limited to reaction products of diols selected frombutane diol, ethylene glycol, propane 1,2 diol, propane 1,3 diol,polyethylene glycol, glycerol, diacids selected from adipic acid,succinic acid, succinic anhydride and hydroxyacids such ashydroxystearic acid, epoxidized soy bean oil, chlorinated paraffins,chlorinated fatty acid esters, fatty acid compounds, plant oils,pigments, and acrylic compounds. The plasticizers may be used eitheralone respectively or in combinations with each other.

In certain embodiments, the compositions and methods of the inventioninclude one or more surfactants. Surfactants are generally used tode-dust, lubricate, reduce surface tension, and/or densify. Examples ofsurfactants include, but are not limited to mineral oil, castor oil, andsoybean oil. One mineral oil surfactant is DRAKEOL® 34, available fromPenreco (Dickinson, Tex., USA). MAXSPERSE® W-6000 and W-3000 solidsurfactants are available from Chemax Polymer Additives (Piedmont, S.C.,USA). Non-ionic surfactants with HLB values ranging from about 2 toabout 16 can be used, examples being TWEEN-20, TWEEN-65, Span-40 andSpan 85.

Anionic surfactants include: aliphatic carboxylic acids such as lauricacid, myristic acid, palmitic acid, stearic acid, and oleic acid; fattyacid soaps such as sodium salts or potassium salts of the abovealiphatic carboxylic acids; N-acyl-N-methylglycine salts,N-acyl-N-methyl-beta-alanine salts, N-acylglutamic acid salts,polyoxyethylene alkyl ether carboxylic acid salts, acylated peptides,alkylbenzenesulfonic acid salts, alkylnaphthalenesulfonic acid salts,naphthalenesulfonic acid salt-formalin polycondensation products,melaminesulfonic acid salt-formalin polycondensation products,dialkylsulfosuccinic acid ester salts, alkyl sulfosuccinate disalts,polyoxyethylene alkylsulfosuccinic acid disalts, alkylsulfoacetic acidsalts, (alpha-olefinsulfonic acid salts, N-acylmethyltaurine salts,sodium dimethyl 5-sulfoisophthalate, sulfated oil, higher alcoholsulfuric acid ester salts, polyoxyethylene alkyl ether sulfuric acidsalts, secondary higher alcohol ethoxysulfates, polyoxyethylene alkylphenyl ether sulfuric acid salts, monoglysulfate, sulfuric acid estersalts of fatty acid alkylolamides, polyoxyethylene alkyl etherphosphoric acid salts, polyoxyethylene alkyl phenyl ether phosphoricacid salts, alkyl phosphoric acid salts, sodium alkylamine oxidebistridecylsulfosuccinates, sodium dioctylsulfosuccinate, sodiumdihexylsulfosuccinate, sodium dicyclohexylsulfosuccinate, sodiumdiamylsulfosuccinate, sodium diisobutylsulfosuccinate, alkylamineguanidine polyoxyethanol, disodium sulfosuccinate ethoxylated alcoholhalf esters, disodium sulfosuccinate ethoxylated nonylphenol halfesters, disodium isodecylsulfosuccinate, disodiumN-octadeeylsulfosuccinamide, tetrasodiumN-(1,2-dicarboxyethyl)-N-octadecylsulfosuccinamide, disodium mono- ordidodecyldiphenyl oxide disulfonates, sodiumdiisopropylnaphthalenesulfonate, and neutralized condensed products fromsodium naphthalenesulfonate.

One or more lubricants can also be added to the compositions and methodsof the invention. Lubricants are normally used to reduce sticking to hotmetal surfaces during processing and can include polyethylene, paraffinoils, and paraffin waxes in combination with metal stearates (e.g., zincsterate). Other lubricants include stearic acid, amide waxes, esterwaxes, metal carboxylates, and carboxylic acids. Lubricants are normallyadded to polymers in the range of about 0.1 percent to about 1 percentby weight, generally from about 0.7 percent to about 0.8 percent byweight of the compound. Solid lubricants is warmed and melted before orduring processing of the blend.

One or more anti-microbial agents can also be added to the compositionsand methods of the invention. An anti-microbial is a substance thatkills or inhibits the growth of microorganisms such as bacteria, fungi,or protozoans, as well as destroying viruses. Antimicrobial drugs eitherkill microbes (microbicidal) or prevent the growth of microbes(microbistatic). A wide range of chemical and natural compounds are usedas antimicrobials, including but not limited to: organic acids,essential oils, cations and elements (e.g., colloidal silver).Commercial examples include but are not limited to PolySept® Z, UDA andAGION®.

PolySept® Z (available from PolyChem Alloy) is a organic salt based,non-migratory antimicrobial. “UDA” is Urtica dioica agglutinin. AGION®antimicrobial is a silver compound. AMICAL® 48 is diiodomethyl p-tolylsulfone. In certain aspects the antimicrobial agent slows downdegradation of the composition.

In film applications of the compositions and methods described herein,anti-lock masterbatch is also added. A suitable example is a slipanti-block masterbatch mixture of erucamide (20% by weight) diatomaceousearth (15% by weight) nucleant masterbatch (3% by weight), pelleted intoPHA (62% by weight).

Cross-Linking Agents

Cross-linking agent, also referred to as co-agents, used in the methodsand compositions of the invention are cross-linking agents comprisingtwo or more reactive functional groups such as epoxides or double bonds.These cross-linking agents modify the properties of the polymer. Theseproperties include, but are not limited to, melt strength or toughness.One type of cross-linking agent is an “epoxy functional compound.” Asused herein, “epoxy functional compound” is meant to include compoundswith two or more epoxide groups capable of increasing the melt strengthof polyhydroxyalkanoate polymers by branching, e.g., end branching asdescribed above.

When an epoxy functional compound is used as the cross-linking agent inthe disclosed methods, a branching agent is optional. As such oneembodiment of the invention is a method of branching a startingpolyhydroxyalkanoate polymer (PHA), comprising reacting a starting PHAwith an epoxy functional compound. Alternatively, the invention is amethod of branching a starting polyhydroxyalkanoate polymer, comprisingreacting a starting PHA, a branching agent and an epoxy functionalcompound. Alternatively, the invention is a method of branching astarting polyhydroxyalkanoate polymer, comprising reacting a startingPHA, and an epoxy functional compound in the absence of a branchingagent. Such epoxy functional compounds can include epoxy-functional,styrene-acrylic polymers (such as, but not limited to, e.g., JONCRYL®ADR-4368 (BASF), or MP-40 (Kaneka)), acrylic and/or polyolefincopolymers and oligomers containing glycidyl groups incorporated as sidechains (such as, but not limited to, e.g., LOTADER® (Arkema),poly(ethylene-glycidyl methacrylate-co-methacrylate)), and epoxidizedoils (such as, but not limited to, e.g., epoxidized soybean, olive,linseed, palm, peanut, coconut, seaweed, cod liver oils, or mixturesthereof, e.g., Merginat® ESBO (Hobum, Hamburg, Germany) and EDENOL® B316 (Cognis, Dusseldorf, Germany)).

For example, reactive acrylics or functional acrylics cross-linkingagents are used to increase the molecular weight of the polymer in thebranched polymer compositions described herein. Such cross-linkingagents are sold commercially. BASF, for instance, sells multiplecompounds under the trade name JONCRYL®, which are described in U.S.Pat. No. 6,984,694 to Blasius et al., “Oligomeric chain extenders forprocessing, post-processing and recycling of condensation polymers,synthesis, compositions and applications”, incorporated herein byreference in its entirety. One such compound is JONCRYL® ADR-4368CS,which is styrene glycidyl methacrylate and is discussed below. Anotheris MP-40 (Kaneka). And still another is Petra line from Honeywell, seefor example, U.S. Pat. No. 5,723,730. Such polymers are often used inplastic recycling (e.g., in recycling of polyethylene terephthalate) toincrease the molecular weight (or to mimic the increase of molecularweight) of the polymer being recycled. Such polymers often have thegeneral structure:

E.I. du Pont de Nemours & Company sells multiple reactive compoundsunder the trade name Elvaloy®, which are ethylene copolymers, such asacrylate copolymers, elastomeric terpolymers, and other copolymers. Onesuch compound is Elvaloy PTW, which is a copolymer of ethylene-n-butylacrylate and glycidyl methacrylate. Omnova sells similar compounds underthe trade names “SX64053,” “SX64055,” and “SX64056.” Other entities alsosupply such compounds commercially.

Specific polyfunctional polymeric compounds with reactive epoxyfunctional groups are the styrene-acrylic copolymers. These materialsare based on oligomers with styrene and acrylate building blocks thathave glycidyl groups incorporated as side chains. A high number of epoxygroups per oligomer chain are used, for example 5, greater than 10, orgreater than 20. These polymeric materials generally have a molecularweight greater than 3000, specifically greater than 4000, and morespecifically greater than 6000. These are commercially available fromS.C. Johnson Polymer, LLC (now owned by BASF) under the trade nameJONCRYL® ADR 4368 material. Other types of polyfunctional polymermaterials with multiple epoxy groups are acrylic and/or polyolefincopolymers and oligomers containing glycidyl groups incorporated as sidechains. A further example of such a polyfunctional carboxy-reactivematerial is a co- or ter-polymer including units of ethylene andglycidyl methacrylate (GMA), available under the trade name LOTADER®resin, sold by Arkema. These materials can further comprise methacrylateunits that are not glycidyl. An example of this type ispoly(ethylene-glycidyl methacrylate-co-methacrylate).

Fatty acid esters or naturally occurring oils containing epoxy groups(epoxidized) can also be used. Examples of naturally occurring oils areolive oil, linseed oil, soybean oil, palm oil, peanut oil, coconut oil,seaweed oil, cod liver oil, or a mixture of these compounds. Particularpreference is given to epoxidized soybean oil (e.g., Merginat® ESBO fromHobum, Hamburg, or EDENOL® B 316 from Cognis, Dusseldorf), but othersmay also be used.

Another type of cross-linking agent are agents with two or more doublebonds. Cross-linking agents with two or more double bond cross-link PHAsby after reacting at the double bonds. Examples of these include:diallyl phthalate, pentaerythritol tetraacrylate, trimethylolpropanetriacrylate, pentaerythritol triacrylate, dipentaerythritolpentaacrylate, diethylene glycol dimethacrylate,bis(2-methacryloxyethyl)phosphate.

In general, it appears that compounds with terminal epoxides may performbetter than those with epoxide groups located elsewhere on the molecule.

Compounds having a relatively high number of end groups are the mostdesirable. Molecular weight may also play a role in this regard, andcompounds with higher numbers of end groups relative to their molecularweight (e.g., the JONCRYL®s are in the 3000-4000 g/mol range) are likelyto perform better than compounds with fewer end groups relative to theirmolecular weight (e.g., the Omnova products have molecular weights inthe 100,000-800,000 g/mol range).

Nucleating Agents

For instance, an optional nucleating agent is added to the compositionto aid in its crystallization. Nucleating agents for various polymersare simple substances, metal compounds including composite oxides, forexample, carbon black, calcium carbonate, synthesized silicic acid andsalts, silica, zinc white, clay, kaolin, basic magnesium carbonate,mica, talc, quartz powder, diatomite, dolomite powder, titanium oxide,zinc oxide, antimony oxide, barium sulfate, calcium sulfate, alumina,calcium silicate, metal salts of organophosphates, and boron nitride;low-molecular organic compounds having a metal carboxylate group, forexample, metal salts of such as octylic acid, toluic acid, heptanoicacid, pelargonic acid, lauric acid, myristic acid, palmitic acid,stearic acid, behenic acid, cerotic acid, montanic acid, melissic acid,benzoic acid, p-tert-butylbenzoic acid, terephthalic acid, terephthalicacid monomethyl ester, isophthalic acid, and isophthalic acid monomethylester; high-molecular organic compounds having a metal carboxylategroup, for example, metal salts of such as: carboxyl-group-containingpolyethylene obtained by oxidation of polyethylene;carboxyl-group-containing polypropylene obtained by oxidation ofpolypropylene; copolymers of olefins, such as ethylene, propylene andbutene-1, with acrylic or methacrylic acid; copolymers of styrene withacrylic or methacrylic acid; copolymers of olefins with maleicanhydride; and copolymers of styrene with maleic anhydride;high-molecular organic compounds, for example: alpha-olefins branched attheir 3-position carbon atom and having no fewer than 5 carbon atoms,such as 3,3dimethylbutene-1,3-methylbutene-1,3-methylpentene-1,3-methylhexene-1,and 3,5,5-trimethylhexene-1; polymers of vinylcycloalkanes such asvinylcyclopentane, vinylcyclohexane, and vinylnorbornane; polyalkyleneglycols such as polyethylene glycol and polypropylene glycol;poly(glycolic acid); cellulose; cellulose esters; and cellulose ethers;phosphoric or phosphorous acid and its metal salts, such as diphenylphosphate, diphenyl phosphite, metal salts of bis(4-tert-butylphenyl)phosphate, and methylene bis-(2,4-tert-butylphenyl)phosphate; sorbitolderivatives such as bis(p-methylbenzylidene) sorbitol andbis(p-ethylbenzylidene) sorbitol; and thioglycolic anhydride,p-toluenesulfonic acid and its metal salts. The above nucleating agentsmay be used either alone or in combinations with each other. Inparticular embodiments, the nucleating agent is cyanuric acid. Incertain embodiments, the nucleating agent can also be another polymer(e.g., polymeric nucleating agents such as PHB).

In certain embodiments, the nucleating agent is selected from: cyanuricacid, carbon black, mica talc, silica, boron nitride, clay, calciumcarbonate, synthesized silicic acid and salts, metal salts oforganophosphates, and kaolin. In particular embodiments, the nucleatingagent is cyanuric acid.

In various embodiments, where the nucleating agent is dispersed in aliquid carrier, the liquid carrier is a plasticizer, e.g., a citriccompound or an adipic compound, e.g., acetylcitrate tributyrate(Citroflex A4, Vertellus, Inc., High Point, N.C.), or DBEEA(dibutoxyethoxyethyl adipate), a surfactant, e.g., Triton X-100,TWEEN-20, TWEEN-65, Span-40 or Span 85, a lubricant, a volatile liquid,e.g., chloroform, heptane, or pentane, a organic liquid or water.

In other embodiments, the nucleating agent is aluminum hydroxydiphosphate or a compound comprising a nitrogen-containingheteroaromatic core. The nitrogen-containing heteroaromatic core ispyridine, pyrimidine, pyrazine, pyridazine, triazine, or imidazole.

In particular embodiments, the nucleating agent can include aluminumhydroxy diphosphate or a compound comprising a nitrogen-containingheteroaromatic core. The nitrogen-containing heteroaromatic core ispyridine, pyrimidine, pyrazine, pyridazine, triazine, or imidazole. Thenucleant can have a chemical formula selected from the group consistingof

and combinations thereof, wherein each R1 is independently H, NR²R²,OR², SR², SOR², SO₂R², CN, COR², CO₂R², CONR²R², NO₂, F, Cl, Br, or I;and each R² is independently H or C₁-C₆ alkyl.

The nucleating agent can be a nucleating agent as described in U.S. Pat.App. Pub. 2005/0209377, by Allen Padwa, which is herein incorporated byreference in its entirety.

Another nucleating agent for use in the compositions and methodsdescribed herein are milled as described in WO 2009/129499 titled“Nucleating Agents for Polyhydroxyalkanoates,” which was published inEnglish and designated the United States, which is herein incorporatedby reference in its entirety. Briefly, the nucleating agent is milled ina liquid carrier until at least 5% of the cumulative solid volume of thenucleating agent exists as particles with a particle size of 5 micronsor less. The liquid carrier allows the nucleating agent to be wetmilled. In other embodiments, the nucleating agent is milled in liquidcarrier until at least 10% of the cumulative solid volume, at least 20%of the cumulative solid volume, at least 30% or at least 40%-50% of thenucleating agent can exist as particles with a particle size of 5microns or less, 2 microns or less or 1 micron or less. In alternativeembodiments, the nucleating agents is milled by other methods, such asjet milling and the like. Additionally, other methods is utilized thatreduce the particle size.

The cumulative solid volume of particles is the combined volume of theparticles in dry form in the absence of any other substance. Thecumulative solid volume of the particles is determined by determiningthe volume of the particles before dispersing them in a polymer orliquid carrier by, for example, pouring them dry into a graduatedcylinder or other suitable device for measuring volume. Alternatively,cumulative solid volume is determined by light scattering.

Application of the Compositions

For the fabrication of useful articles, the compositions describedherein are processed preferably at a temperature above the crystallinemelting point of the polymers but below the decomposition point of anyof the ingredients (e.g., the additives described above, with theexception of some branching agents) of the polymeric composition. Whilein heat plasticized condition, the polymeric composition is processedinto a desired shape, and subsequently cooled to set the shape andinduce crystallization. Such shapes can include, but are not limited to,a fiber, filament, film, sheet, rod, tube, bottle, or other shape. Suchprocessing is performed using any art-known technique, such as, but notlimited to, extrusion, injection molding, compression molding, blowingor blow molding (e.g., blown film, blowing of foam), calendaring,rotational molding, casting (e.g., cast sheet, cast film), orthermoforming.

The compositions are used to create, without limitation, a wide varietyof useful products, e.g., automotive, consumer durable, construction,electrical, medical, and packaging products. For instance, the polymericcompositions is used to make, without limitation, films (e.g., packagingfilms, agricultural film, mulch film, erosion control, hay bale wrap,slit film, food wrap, pallet wrap, protective automobile and appliancewrap, etc.), golf tees, caps and closures, agricultural supports andstakes, paper and board coatings (e.g., for cups, plates, boxes, etc.),thermoformed products (e.g., trays, containers, lids, yoghurt pots, cuplids, plant pots, noodle bowls, moldings, etc.), housings (e.g., forelectronics items, e.g., cell phones, PDA cases, music player cases,computer cases and the like), bags (e.g., trash bags, grocery bags, foodbags, compost bags, etc.), hygiene articles (e.g., diapers, femininehygiene products, incontinence products, disposable wipes, etc.),coatings for pelleted products (e.g., pelleted fertilizer, herbicides,pesticides, seeds, etc.), injection molded articles (writinginstruments, utensils, disk cases, etc.), solution and spun fibers andmelt blown fabrics and non-wovens (threads, yarns, wipes, wadding,disposable absorbent articles), blow moldings (deep containers, bottles,etc.) and foamed articles (cups, bowls, plates, packaging, etc.).

Thermoforming is a process that uses films or sheets of thermoplastic.The polymeric composition is processed into a film or sheet. The sheetof polymer is then placed in an oven and heated. When soft enough to beformed it is transferred to a mold and formed into a shape.

During thermoforming, when the softening point of a semi-crystallinepolymer is reached, the polymer sheet begins to sag. The window betweensoftening and droop is usually narrow. It can therefore be difficult tomove the softened polymer sheet to the mold quickly enough. Branchingthe polymer can be used to increase the melt strength of the polymer sothat the sheet maintains is more readily processed and maintains itsstructural integrity. Measuring the sag of a sample piece of polymerwhen it is heated is therefore a way to measure the relative size ofthis processing window for thermoforming.

Because the composition described herein have increased melt strengthand increased processability, they are easier to convert to film orsheet form. They are therefore excellent candidates for thermoforming.Molded products include a number of different product types and, forexample, including products such as disposable spoons, forks and knives,tubs, bowls, lids, cup lids, yogurt cups, and other containers, bottlesand bottle-like containers, etc.

The compositions described herein can be processed into films of varyingthickness, for example, films of uniform thickness ranging from 10-200microns, for example, 20-75 microns, 75 to 150 microns, or from 50-100microns. Film layers can additionally be stacked to form multilayerfilms of the same or varying thicknesses or compositions. For example, afilm can comprise two, three, four or more layers, where the layers caninclude one or more layers of a composition of the invention combinedwith other polymer layers, such as PHA layers, or PLA layers and thelike.

Blow molding, which is similar to thermoforming and is used to producedeep draw products such as bottles and similar products with deepinteriors, also benefits from the increased elasticity and melt strengthand reduced sag of the polymer compositions described herein.

Articles made from the compositions can be annealed according to any ofthe methods disclosed in WO 2010/008445, and titled “Branched PHACompositions, Methods For Their Production, And Use In Applications,”which was filed in English and designated the United States. Thisapplication is incorporated by reference herein in its entirety.

The compositions described herein are provided in any suitable formconvenient for an intended application. For example, the composition isprovided in pellet for subsequent production of films, coatings,moldings or other articles, or the films, coatings, moldings and otherarticles.

The specific examples below are to be construed as merely illustrative,and not limitative of the remainder of the disclosure in any waywhatsoever. Without further elaboration, it is believed that one skilledin the art can, based on the description herein, utilize the presentinvention to its fullest extent. All publications cited herein arehereby incorporated by reference in their entirety.

EXAMPLES

Experimental Methods

Measurement of Torsional Melt Rheology (G′)

All oscillatory rheology measurements were performed using a TAInstruments AR2000 rheometer employing a strain amplitude of 1%. First,pellets (or powder) were molded into 25 mm diameter discs that wereabout 1200 microns in thickness. The disc specimens were molded in acompression molder set at about 165° C., with the molding time of about30 seconds. These molded discs were then placed in between the 25 mmparallel plates of the AR2000 rheometer, equilibrated at 180° C., andsubsequently cooled to 160° C. for the frequency sweep test. A gap of800-900 microns was used, depending on the normal forces exerted by thepolymer. The melt density of PHB was determined to be about 1.10 g/cm³at 160° C.; this value was used in all the calculations.

Specifically, the specimen disc is placed between the platens of theparallel plate rheometer set at 180° C. After the final gap is attained,excess material from the sides of the platens is scraped. The specimenis then cooled to 160° C. where the frequency scan (from 625 rad/s to0.10 rad/s) is then performed; frequencies lower than 0.1 rad/s areavoided because of considerable degradation over the long time it takesfor these lower frequency measurements. The specimen loading, gapadjustment and excess trimming, all carried out with the platens set at180° C., takes about 2½ minutes. This is controlled to within ±10seconds to minimize variability and sample degradation. Cooling from180° C. to 160° C. (test temperature) is accomplished in about fourminutes. Exposure to 180° C. ensures a completely molten polymer, whiletesting at 160° C. ensures minimal degradation during measurement.

During the frequency sweep performed at 160° C., the following data arecollected as a function of measurement frequency: |n*| or complexviscosity, G′ or elastic modulus (elastic or solid-like contribution tothe viscosity) and G″ or loss modulus (viscous or liquid-likecontribution to the viscosity). For purposes of simplicity, we will useG′ measured at an imposed frequency of 0.25 rad/s as a measure of “meltstrength”. Higher G′ translates to higher melt strength.

Measurement of Capillary Stability

The Capillary Stability was measured by performing steady shearexperiments at 180° C. using a Kayness Galaxy V Capillary Rheometer. Thedie employed in the above capillary measurements was about 1.0 mm indiameter and about 30 mm in length. The capillary rheometer is acontrolled shear rate device, and was operated at three shear rates(1,000 sec⁻¹, 100 sec⁻¹, and 10 sec⁻¹), repeated three times, for atotal of nine (9) data points collected over 17 minutes. The pellets(˜10 grams) were preheated at 180° C. for 240 seconds (4 minutes) beforethe start of the test. The nine test data points are collected withoutany delay between them.

Because PHB copolymers undergo chain scission reactions in the melt thatlead to a continuous decrease in melt viscosity as a function of time,the above test protocol generates data as shown below (see FIG. 1 for arepresentative PHB copolymer).

When log (Apparent Viscosity) is plotted as a function of time, asystematic decrease in viscosity is evident; this trend is also noted tobe quite linear. The slope of the “Apparent Viscosity Versus Time” fityields is an indication of melt stability (according to ASTM D3835). Inthis report, we use this slope for data collected at a shear rate of 100s-1 as an indication of melt stability and this slope is referred to asthe “Capillary Stability”.

Measurement of Melt Crystallization

A Perkin Elmer DSC is used to characterize the non-isothermalmelt-crystallization kinetics of the subject PHB copolymers. In thistest, the specimen (cut from a disc compression molded at 165° C. forone minute) is placed and crimped in the DSC sample pan. This testspecimen is then exposed to 200° C. for one minute to melt all of thecrystals; it is then cooled to 160° C. at 40° C./min and maintained at160° C. for about 1 minute. The specimen is then cooled to −50° C. at arate of about 10° C./min. As the polymer undergoes crystallization, anexothermic peak in the “heat flow versus temperature” trace becomesevident. The peak-temperature of this exotherm is noted as thecrystallization temperature or Tmc. A higher Tmc generally means fastercrystallization kinetics.

Measurement of Mechanical Properties of Blown Film

The Elmendorf resistance to tear propagation was measured according toASTM D1922-06. The tear propagation resistance of the film was measuredin two directions, along the flow exiting the die (“machine directiontear” or “MD Tear”) and also perpendicular to the polymer flow exitingthe die (“transverse direction tear” or “TD Tear”).

The dart impact strength was measured according to ASTM D1709-04.

The tensile properties (i.e., modulus, strength, elongation to break)were measured according to ASTM D882-02.

Measurement of the Mechanical Properties of Injection Molded Articles

Tensile properties of injection molded articles were measured accordingto ASTM D638-03.

Flexural properties of injection molded articles were measured accordingto ASTM D790-03.

Notched Izod properties of injection molded articles were measuredaccording to ASTM D256-06.

Soil Biodegradation Test Method

The biodegradation rate of the subject films was characterized andquantified using a soil burial test. In this test, a small piece of thefilm specimen (˜5 cm by 9 cm) was buried under 1-2 inches of soil in aplastic container inside a room where the temperature was maintainedbetween 20-25C. The soil was a top soil obtained from a local commercialvegetable farm in Massachusetts. The soil moisture content wasmaintained by watering regularly (7 grams of water was added to about100 grams of soil once every three days). Since the container was notcovered, the moisture content in the soil dropped from about 9-10% to1-2% in three days. The buried film specimens are retrieved on a weeklybasis (different specimen for each week of elapsed time buried in soil);the retrieved specimens are first washed with water to remove dirt andthen dried with paper towels. The dried film specimens (or fragments, ifconsiderable biodegradation had already occurred) are weighed. Themeasured weight loss quantifies the rate of biodegradation for thedifferent formulations. In Examples presented in this application, thefilm specimen geometry is kept constant; consequently, the absolutevalue of the weight loss provides an accurate depiction of thebiodegradation kinetics. A higher weight loss translates to fasterbiodegradation.

Example 1 Compositions Containing PHA Blends and Poly(ButyleneSuccinate)

In this Example, compositions that include a PHA copolymer and PBS(BIONOLLE® 1001 from Showa Highpolymer Co., Ltd., Japan) were preparedby dry-blending the components at a pre-determined ratio and subjectingthis mixture to twin-screw extrusion in a ¾ inch Brabender extruderoperated at about 50 rpm and a melt temperature of about 180° C. Theformulations are indicated in the table below.

TABLE 1 Compositions containing PHA blend and PBS 1 2 3 4 5 6 7 8 9Formulation PHA Blend 97 92 87 77 62 47 32 17 0 (wt %) Nuc. MB 3 3 3 3 33 3 3 0 (wt %) PBS (wt %) 0 5 10 20 35 50 65 80 100 Total 100 100 100100 100 100 100 100 100 Data: G′ (@ 0.25 51 74 48 103 170 202 363 6591288 rad/s) Eta* (@ 2937 3122 2517 2846 3761 4179 5119 7081 12920 0.25rad/s) Capillary −0.10 −0.08 −0.08 −0.09 −0.08 −0.10 −0.09 −0.06 −0.02Stability Tmc (PHA 113.4 107.9 108.2 107.9 103.2 100.4 102.0 99.1 —Blend) Tmc (PBS) — nd nd nd 85.6 85.3 87.2 86.2 87.1 “nd” = notdetectable

The PHA blend was composed of about 58-62% homo-polymer of3-hydroxybutanoic acid, and about 38-42% copolymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 8-14% weight percent. The nucleating masterbatch (“Nuc.MB”) was cyanuric acid that had been previously compounded at a rate of33% (by weight) into a base resin of 3-hydroxybutanoic acid and4-hydroxybutanoic acid, and pelleted. The PBS was BIONOLLE® 1001 (ShowaHighpolymer Co., Ltd., Japan).

Formulation 1 is the PHA control (no PBS). Formulation 2 is the PBScontrol (no PHA blend). The PHA control displays considerably lower meltviscosity (Eta*) and melt strength (G′) compared to PBS. The meltstability (capillary stability) of the PHA is also worse compared tothat of PBS. G′ and capillary stability for the formulations are plottedas a function of formulation composition below. These parameters appearto be quite independent of formulation composition when PBS is the minorcomponent and strongly dependent on formulation composition when PBS isthe major component. In other words, the increase in G′ with increasinglevels of the higher melt strength PBS in the blend is very modest up toa formulation composition of about 50% PBS. As the concentration of PBSin these formulations is increased further, the increase in G′ becomessignificant as it approaches the G′ of the pure PBS. In terms ofcapillary stability, PBS is considerably more stable compared to thepure PHA. The capillary stability of all formulations with PHA as themajor component is very similar to that of the PHA control; however,when PBS becomes the major component, a systematic improvement instability is evident with increasing levels of PBS. The crystallizationrate (Tmc) of PHA decreases slightly in the presence of PBS; however,Tmc does not appear to depend on PBS concentration. All of the data forthis particular formulation series indicate a multi-phase melt with verylittle miscibility between the PHA and PBS. See FIG. 2 and FIG. 3.

Example 2 Compositions Containing PHA Blends and Polybutylene SuccinateAdipate

In this Example, formulations of a PHA copolymer and PBSA (BIONOLLE®3001 from Showa Highpolymer Co., Ltd., Japan) were prepared bydry-blending the components at a pre-determined ratio and subjectingthis mixture to twin-screw extrusion in a ¾ inch Brabender extruderoperated at about 50 rpm and a melt temperature of about 180° C. Thecompositions of the formulations are indicated in the table below.

TABLE 2 Compositions containing PHA blend and PBSA 1 2 3 4 5 6 7 8 9Formulation PHABlend 97 92 87 77 62 47 32 17 0 (wt %) Nuc. MB 3 3 3 3 33 3 3 0 (wt %) PBSA 0 5 10 20 35 50 65 80 100 (wt %) Total 100 100 100100 100 100 100 100 100 Data: G′ (@0.25 51 64 72 108 133 133 300 10091383 rad/s) Eta* (@ 2937 2931 2834 2787 3274 3392 4902 9284 13560 0.25rad/s) Capillary −0.10 −0.10 −0.09 −0.09 −0.11 −0.11 −0.08 −0.04 −0.02Stability Tmc (PHA 113.4 108.4 109.0 107.3 103.6 103.0 100.0 nd — Blend)Tmc — nd nd nd 65.0 63.3 62.3 62.3 65.0 (PBSA) “nd” = not detectable

The PHA blend was composed of about 58-62% homo-polymer of3-hydroxybutanoic acid, and about 38-42% co-polymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 8-14% weight percent. The nucleating masterbatch (“Nuc.MB”) was cyanuric acid that had been previously compounded at a rate of33% (by weight) into a base resin of 3-hydroxybutanoic acid and4-hydroxybutanoic acid, and pelleted. The PBSA was BIONOLLE® 3001 (ShowaHighpolymer Co., Ltd., Japan).

Formulation 1 is the PHA control (no PBSA). Formulation 9 is the PBSAcontrol (no PHA Blend). The PHA control displays considerably lower meltviscosity and melt strength compared to PBSA. The melt stability of thePHA is also worse compared to that of PBSA. G′ and capillary stabilityfor the formulations are plotted as a function of formulationcomposition below. These parameters appear to be quite independent offormulation composition when PBSA is the minor component and stronglydependent on formulation composition when PBSA is the major component.In other words, the increase in G′ with increasing levels of the highermelt strength PBSA in the formulation is very modest up to a formulationcomposition of about 50% PBSA. As the concentration of PBSA in theseformulations is increased further, the increase in G′ becomessignificant as it approaches the G′ of the pure PBSA. In terms ofcapillary stability, PBSA is considerably more stable compared to thepure PHA. The capillary stability of all formulations with PHA as themajor component is very similar to that of the PHA control; however,when PBSA becomes the major component, a systematic improvement instability is evident with increasing levels of PBSA. The crystallizationrate (Tmc) of PHA decreases slightly in the presence of PBSA; however,Tmc does not appear to depend on PBSA concentration. All of the data forthis particular formulation series indicate a multi-phase melt with verylittle miscibility between the PHA and PBSA. Finally, formulations ofPHA with PBS behaved quite similar to formulations of PHA and PBSA. SeeFIG. 4 and FIG. 5.

Example 3 Compositions Containing PHA Blends and PBS Combined withOrganic Peroxide

In Examples 1 and 2, blends of PHA with either PBS or PBSA were preparedusing simple melt-extrusion. The melt rheology of these formulationsindicated the existence of two distinct phases in the melt, with therheological signature of the major formulation component dominating theoverall response. In this example, blends of PHA with PBS are presented,where the melt-blending was carried out in the presence of an organicperoxide. A common plasticizer, CITROFLEX® A4, was also included inthese formulations. All of the components for each formulation werephysically mixed at a pre-determined ratio, and this mixture was thensubjected to twin-screw extrusion in a ¾″-inch Brabender extruderoperated at about 50 rpm and a melt temperature of about 180° C. Theformulation compositions are indicated in the table below.

TABLE 3 Compositions containing PHA blend, PBS and organic peroxide 1 2Formulation PHA Blend (wt %) 72 72 Nuc. MB (wt %) 3 3 Citroflex A4 5 4.8Peroxide (wt %) 0 0.2 PBS (wt %) 20 20 Total 100 100 Data: G′ (@ 0.25rad/s) 148 865 Eta* (@ 0.25 rad/s) 3380 7342 Capillary Stability 0 0.14−0.12 Tmc (PHA Blend) 103.1 105.0 Tmc (PBS) 84.0 85.7

The PHA blend was composed of about 58-62% homo-polymer of3-hydroxybutanoic acid, and about 38-42% co-polymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 8-14% weight percent. The nucleating masterbatch (“Nuc.MB”) was cyanuric acid that had been previously compounded at a rate of33% (by weight) into a base resin of 3-hydroxybutanoic acid and4-hydroxybutanoic acid, and pelleted. The peroxide wastert-butylperoxy-2-ethylhexylcarbonate (available from Akzo Nobel asTRIGANOX® 117). The PBS was BIONOLLE® 1001 (Showa Highpolymer Co., Ltd.,Japan).

Formulation 1 is the first control with about 20 weight percent PBS.Formulation 2 is similar in composition to Formulation 1 with theexception of about 0.2 percent of an organic peroxide (TRIGANOX® 117)pre-dissolved in CITROFLEX® A4 prior to the mixing of the formulationcomponents. Formulation 2 displays considerably higher melt strength(G′) and better melt stability (smaller capillary stability) compared toFormulation 1; further, the PHA and PBS appear to crystallize at highertemperatures in formulations prepared with peroxide. The melt rheology(complex viscosity versus angular frequency) for Formulation 1 and 2 areshown in FIG. 6; the data for the corresponding PHA control (Formulation1 from Examples 1 and 2) and the PBS are also. In this figure, thecontrol formulation for this example, Formulation 1, shows rheologicalbehavior very similar to that of the PHA control. However, therheological signature of Formulation 2 appeared to be in between thoseof the PHA control and the PBS control. In other words, the formulationprepared using reactive extrusion (in the presence of an organicperoxide) showed rheological characteristics intermediate to those ofthe PHA and PBS controls. See FIG. 6.

Example 4 Compositions Containing PHA Blends and PBSA Combined withOrganic Peroxide

This example is very similar to Example 3, except that PBSA (BIONOLLE®3001) was used in place of PBS (BIONOLLE® 1001).

TABLE 4 Compositions containing PHA blend, PBSA and organic peroxide 1 2Formulation PHA Blend (wt %) 72 72 Nuc. MB (wt %) 3 3 Citroflex A4 5 4.8Peroxide (wt %) 0 0.2 PBSA (wt %) 20 20 Total 100 100 Data: G′ (@ 0.25rad/s) 105 398 Eta* (@ 0.25 rad/s) 3080 4659 Capillary Stability 0 0.14−0.11 Tmc (PHA Blend) 106.0 107.3 Tmc (PBSA) nd nd “nd” = not detectable

The PHA blend was composed of about 58-62% homo-polymer of3-hydroxybutanoic acid, and about 38-42% co-polymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 8-14% weight percent. The nucleating masterbatch (“Nuc.MB”) was cyanuric acid that had been previously compounded at a rate of33% (by weight) into a base resin of 3-hydroxybutanoic acid and4-hydroxybutanoic acid, and pelleted. The peroxide wastert-butylperoxy-2-ethylhexylcarbonate (available from Akzo Nobel asTRIGANOX® 117). The PBSA was BIONOLLE® 3001 (Showa Highpolymer Co.,Ltd., Japan).

In Examples 1 and 2, blends of PHA with either PBS or PBSA were preparedusing simple melt-extrusion. The melt rheology of these formulationsindicated the existence of two distinct phases in the melt, with therheological signature of the major formulation component dominating theoverall response. In this example, combinations of PHA with PBSA arepresented wherein the melt-blending was carried out in the presence ofan organic peroxide. A common plasticizer, CITROFLEX® A4, was alsoincluded in these formulations. All of the components for eachformulation were physically mixed at a pre-determined ratio; thismixture was subjected to twin-screw extrusion in a ¾ inch Brabenderextruder operated at about 50 rpm and a melt temperature of about 180°C. The compositions are indicated in the table above. Formulation 1 isthe first control with about 20 weight percent PBSA. Formulation 2 issimilar in composition to Formulation 1 with the exception of about 0.2percent of an organic peroxide (TRIGANOX® 117) pre-dissolved inCITROFLEX® A4 prior to the mixing of the formulation components.Formulation 2 displays considerably higher melt strength (G′) and bettermelt stability (smaller capillary stability) compared to Formulation 1;further, the PHA crystallizes at higher temperature in formulationsprepared with peroxide.

The observations presented in this Example are largely similar to thosepresented in Example 3. In summary, when PHA/PBSA formulations areprepared by simple melt-extrusion, their melt rheology suggest amulti-phase melt with the major formulation component dominating theresponse on a rheological length scale. In contrast, when the sameformulations are prepared using reactive melt-extrusion, the rheologicalresponse indicate a single-phase melt with some unexpected benefits inmelt strength and melt stability. The PHA phase also crystallizes at ahigher temperature when the formulation is prepared using reactiveextrusion.

Examples 3 and 4 show the distinct melt rheological advantages (highermelt strength and superior melt stability) when blends of PHA and PBS orPBSA are created using reactive melt-extrusion in the presence of verysmall amounts of an organic peroxide. The improvements noted in meltstrength and capillary stability (melt stability) are unexpected andvery advantageous (melt properties for making films and relatedmaterial).

Reactive melt extrusion is studied further in the subsequent examples.

Example 5 Films Containing PHA/PBSA Blends Melt-Compounded in thePresence of an Organic Peroxide

In Examples 1 and 2, the characteristics of PHA/PBS and PHA/PBSAformulations prepared by simple melt-blending were discussed. The meltrheology of these formulations indicated poor miscibility between thetwo polymers with the rheology of the major component dominating theoverall response. In Examples 3 and 4, it was shown that when PHA/PBSand PHA/PBSA formulations are prepared by melt-blending in the presenceof a reactive compound such as an organic peroxide, some synergisticrheological observations are evident. These formulations, created in areactive environment, displayed considerably higher melt strength andbetter melt stability compared to formulations created without peroxide;the PHA phase also crystallizes at a higher temperature in theseformulations.

The present example is an extension of Example 4, wherein a differentPHA is melt-compounded with PBSA in the presence of an organic peroxideand a branching co-agent. The relative proportions of the PHA and PBSAphases were varied while all other additives (plasticizer, mineralfillers) were kept unchanged. The compositions are described in tablebelow. These compositions were created using a 27 mm MAXX Leistritzco-rotating twin-screw extruder with the 10 barrel and die zones set at175/175/170/170/170/165/165/165/160/160(° C.). Other compounding dataand conditions are also listed in the table.

TABLE 5 Compositions containing PHA blend, PBSA and organic peroxide 1 23 4 PBSA Formulation PHA Blend (wt %) 79 71 59 47 PBSA (wt %) 0 8 20 32Nuc. MB (wt %) 3 3 3 3 Slip/Antiblock MB (wt %) 5 5 5 5 Citroflex A4 (wt%) 7.75 7.75 7.75 7.75 Peroxide (wt %) 0.15 0.15 0.15 0.15 PE3A (wt %)0.10 0.10 0.10 0.10 CaCO3 (wt %) 5 5 5 5 Total 100 100 100 100Compounding Data: Screw RPM 125 125 150 150 Rate (lbs/hr) 85 85 75 75Melt Temp (° C.) 189 196 204 209 Melt Pressure (psi) 2321 2395 2530 2649Load (%) 46 46 40 41 Data: G′ (@ 0.25 rad/s) 549 689 1413 2584 1383 Eta*(@ 0.25 rad/s) 6975 7380 8749 13420 13560 Capillary Stability −0.09−0.08 −0.06 −0.06 −0.02 Tmc (PHA Blend) 105.9 103.4 101.8 99.1 — Tmc(PBSA) — nd 60.2 64.3 65.0 Film MD Tear (g) 18.2 32.8 38 39.4 24 Film TDTear (g) 29.8 36 42 45.6 32 Film Dart Impact (g) 25 52 59 70 200 Film MDModulus (MPa) 395 369 359 306 320 Film MD Break Strength (MPa) 18.5 21.823 22.8 40.0 Soil Biodegradation 0.207 0.117 0.085 0.054 0.031 (Wt lossafter 5 weeks (grams))

The PHA blend was composed of about 34-38% homo-polymer of3-hydroxybutanoic acid, and about 22-26% co-polymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 8-14 weight percent, and about 38-42% co-polymer of3-hydroxybutanoic acid and 4-hydroxybutanoic acid with the4-hydroxybutanoic acid composition being nominally 25-33 weight percent.The nucleating masterbatch (“Nuc. MB”) was cyanuric acid that had beenpreviously compounded at a rate of 33% (by weight) into a base resin of3-hydroxybutanoic acid and 4-hydroxybutanoic acid, and pelleted. Theslip anti-block masterbatch was a mixture of erucamide (20% by weight)diatomaceous earth (15% by weight) nucleant masterbatch (3% by weight),pelleted into PHA (62% by weight). The peroxide wastert-butylperoxy-2-ethylhexylcarbonate (available from Akzo Nobel asTRIGANOX® 117). The PBSA was BIONOLLE® 3001 (Showa Highpolymer Co.,Ltd., Japan). “PE3A” is pentaerythritol triacrylate. The CaCO3 wascalcium carbonate (EMFORCE® Bio, available from (Specialty MineralsInc., Bethlehem, Pa., USA).

The table above lists the measured properties for the variousformulations prepared. Formulation 1 is the control sample without anyPBSA, while Formulations 2, 3, and 4 contain 8, 20 and 32 weight percentPBSA in the formulation. In FIG. 8, G′ and capillary stability are shownas a function of composition for the samples from this example and forsamples from Example 2 (non-reactive formulation counterparts). Theadvantages of combining in the presence of a reactive compound aredistinct and surprising. The melt strength and melt stability areconsiderably superior for formulations created using reactive extrusion.In fact, both G′ and capillary stability for these formulations arestatistically better than what one might predict using a simplerule-of-mixtures trend. See FIG. 7 and FIG. 8.

The blends from this example (including pure PBSA) were also convertedinto blown film for further characterization. The blown films were madeusing a 1.5 inch 24:1 Davis Standard extruder fitted with a 2.5 inchspiral mandrel die and a Future Design dual-lip air ring. Thetemperature setting on the extruder was 350/345/340/330(° F.) and thedie was set at 335° F. The extruder was operated at 40 rpm with a diegap setting of about 40 mils. The films collected were about 2 mils inthickness at a blow-up ratio of about 2.5.

The film properties, particularly tear resistance, of the PHA/PBSAformulations created using reactive extrusion are considerably betterthan that of the PHA control and the PBSA control. This is anothersynergistic observation from such reactive blends. Another advantage ofblending PBSA with PHA is the considerably slower rate of biodegradationof the resultant films relative to the PHA control. The soilbiodegradation results for the reactive blend films, after 5 weeks insoil, show considerably lower weight loss compared to the control film.

Example 6 Films Containing PHA Blends and PBS Combined with OrganicPeroxide

This example is largely similar to Example 5 and is somewhat of anextension to Example 3. Here, a different PHA is melt-compounded withPBS in the presence of an organic peroxide and a branching co-agent. Therelative proportions of the PHA and PBS phases were varied while allother additives (plasticizer, mineral fillers) were kept unchanged. Thecompositions of these formulations are described in table below. Theseformulations were created using a 27 mm MAXX Leistritz co-rotatingtwin-screw extruder with the 10 barrel and die zones set at175/175/170/170/170/165/165/165/160/160(° C.). Other compounding dataand conditions are also listed in the table.

TABLE 6 Compositions containing PHA blend, PBS and organic peroxide 1 23 4 PBSA Formulation PHA Blend (wt %) 79 71 59 47 PBS (wt %) 0 8 20 32Nuc. MB (wt %) 3 3 3 3 Slip/Antiblock MB (wt %) 5 5 5 5 CITROFLEX ® A4(wt %) 7.75 7.75 7.75 7.75 Peroxide (wt %) 0.15 0.15 0.15 0.15 PE3A (wt%) 0.10 0.10 0.10 0.10 CaCO3 (wt %) 5 5 5 5 Total 100 100 100 100Compounding Data: Screw RPM 125 125 150 150 Rate (lbs/hr) 85 85 75 75Melt Temp (° C.) 189 195 202 209 Melt Pressure (psi) 2321 2415 2579 2632Load (%) 46 46 40 41 Data: G′ (@ 0.25 rad/s) 549 785 1390 2950 1288 Eta*(@ 0,25 rad/s) 6975 7818 9002 15020 12920 Capillary Stability −0.09−0.08 −0.06 −0.06 −0.02 Tmc (PHA Blend) 105.9 101.5 100.5 100.0 — Tmc(PBS) — nd 83.2 86.7 87.1 Film MD Tear (g) 18.2 24.8 34 34.2 — Film TDTear (g) 29.8 32 38.4 34.8 — Film Dart Impact (g) 25 46 63 49 — Film MDModulus (MPa) 395 407 391 362 — Film MD Break Strength (MPa) 18.5 17.223 26.4 — Soil Biodegradation 0.207 0.115 0.075 0.049 — (Wt loss after 5weeks (grams)) “nd” = not detectable

The PHA blend was composed of about 34-38% homo-polymer of3-hydroxybutanoic acid, and about 22-26% co-polymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 8-14 weight percent, and about 38-42% co-polymer of3-hydroxybutanoic acid and 4-hydroxybutanoic acid with the4-hydroxybutanoic acid composition being nominally 25-33 weight percent.The nucleating masterbatch (“Nuc. MB”) was cyanuric acid that had beenpreviously compounded at a rate of 33% (by weight) into a base resin of3-hydroxybutanoic acid and 4-hydroxybutanoic acid, and pelleted. Theslip anti-block masterbatch was a mixture of erucamide (20% by weight)diatomaceous earth (15% by weight) nucleant masterbatch (3% by weight),pelleted into PHA (62% by weight). The peroxide wastert-butylperoxy-2-ethylhexylcarbonate (available from Akzo Nobel asTRIGANOX® 117). The PBS was BIONOLLE® 1000 (Showa Highpolymer Co., Ltd.,Japan). “PE3A” is pentaerythritol triacrylate. The CaCO3 was calciumcarbonate (EMFORCE® Bio, available from (Specialty Minerals Inc.,Bethlehem, Pa., USA).

The table above lists the measured properties for the variousformulations prepared. Formulation 1 is the control sample without anyPBSA, while Formulation 2, 3, and 4 contain 8, 20 and 32 weight percentPBS in the formulation. Similar to the observations for Example 5, theadvantages of combining in the presence of a reactive compound aredistinct and surprising. The melt strength and melt stability areconsiderably superior for the formulations created using reactiveextrusion, much better than a rule-of-mixtures prediction.

The formulations from this example were also converted into blown filmfor further characterization. The blown films were made using a 1.5 inch24:1 Davis Standard extruder fitted with a 2.5 inch spiral mandrel dieand a Future Design dual-lip air ring. The temperature setting on theextruder was 350/345/340/330(° F.) and the die was set at 335° F. Theextruder was operated at 40 rpm with a die gap setting of about 40 mils.The films collected were about 2 mils in thickness at a blow-up ratio ofabout 2.5.

The film properties, particularly tear resistance and dart impactresistance, of the PHA/PBSA formulations created using reactiveextrusion are considerably better than that of the PHA control. Anotheradvantage of combining PBSA with PHA is the considerably slower rate ofbiodegradation of the resultant films relative to the PHA control. Thesoil biodegradation results for the reactive formulation films, after 5weeks in soil, show considerably lower weight loss compared to thecontrol film.

Example 7 Injection Molded Articles Containing PHA Blends and PBS

In this example, PHA blend injection molding formulations were made thatalso included PBS. The formulations began with production of aninjection molding composition containing PHA Blend 73% by weight,Acrawax C concentrate (50% active) 1% by weight, talc 11% by weight(FLEXTALC® 610D, available from Specialty Minerals Inc., Bethlehem, Pa.,USA), calcium carbonate 10% by weight (MULTIFEX-MM®, available fromSpecialty Minerals Inc., Bethlehem, Pa., USA), and nucleatingmasterbatch 5% by weight. The PHA blend was composed of about 58-62%homo-polymer of 3-hydroxybutanoic acid, and about 38-42% co-polymer of3-hydroxybutanoic acid and 4-hydroxybutanoic acid, where the4-hydroxybutanoic acid is approximately 8-14% weight percent. Thenucleating agent is cyanuric acid dispersed at a rate of 33% (by weight)in CITROFLEX® A4 plasticizer and milled.

This injection molding composition was then dry-blended with PBS, orwith PBS and peroxide. The peroxide wastert-butylperoxy-2-ethylhexylcarbonate (available from Akzo Nobel asTRIGANOX® 117). The PBS was BIONOLLE® 1001 (Showa Highpolymer Co., Ltd.,Japan). The formulations are shown in the table below.

TABLE 7 Compositions containing PHA blend, PBS and organic peroxide 1 23 Formulation IM Composition (wt %) 100 70 69.9 PBS (wt %) 0 30 30Peroxide (wt %) 0 0 0.1 Total 100 100 100 Compounding: Pressure (psi)1708 1589 3028 Load (%) 45 39 48 Melt Temp (° C.) 203 202 211 Data:Tensile Strength (Mpa) 25.68 27.52 29.41 Tensile Modulus (Mpa) 2765 17751747 Tensile Elongation (%) 4.07 11.49 17.41 Flexural Strength (Mpa)46.14 40.03 41.07 Flexural Modulus (Mpa) 2872 1853 1832 Notched IzodImpact 0.528 0.735 0.859 Strength (ft-lb/in) Onset Crystallization 118.4107.4 109.6 Temperature (° C.) Peak Crystallization 113.89 103.81 105.49Temperature (° C.) Zero Time Melt 1447 1534 1919 Viscosity, 100 s−1 (Pa· s) Five Minute Melt 894 1186 1523 Viscosity, 100 s−1 (Pa · s) MeltStability (min−1) −0.0962 −0.0515 −0.0462 G′ (0.25 rad/s) (Pa) 115.91712 7887 Eta * (0.25 rad/s) (Pa · s) 3540 15200 37140

The above formulations were compounded using a 27 mm Leistritztwin-screw extruder using the following temp-profile:175/175/175/175/170/170/170/170/170/180(° C.); the formulations weremade at 60 lbs/hr rate and 125 screw rpm.

All tensile properties were measured according to ASTM D638-03. Allflexural properties were measured according to ASTM D790-03. NotchedIzod impact strength was measured according to D256-06.

As shown above, tensile strength, tensile elongation and notched Izodwere improved by addition of PBS, especially when melt-blended in thepresence of a reactive compound, but tensile modulus, and flexuralmodulus and strength were negatively affected.

Melt stability, G′ and Eta* were also greatly improved by addition ofPBS, especially when melt-blended in the presence of a reactivecompound.

The table above summarizes the melt rheology of the compounded pelletsand the mechanical properties of injection molded bars from the aboveformulations. The advantages of combining PBS with PHA blends in thepresence of peroxide are distinct as evident in G′, melt capillarystability, tensile strength, tensile elongation and impact strength.

Example 8 Injection Molded Articles Containing PHA Blends and PBS

In this example, a slightly different injection molding composition wascombined with PBS.

The formulations began with production of an injection moldingcomposition containing PHA Blend 73.21% by weight, Acrawax C concentrate(50% active) 0.36% by weight, talc 11.66% by weight (FLEXTALC® 610D,available from Specialty Minerals Inc., Bethlehem, Pa., USA), calciumcarbonate 10.2% by weight (EMFORCE® Bio, available from SpecialtyMinerals Inc., Bethlehem, Pa., USA), and nucleating masterbatch 4.57% byweight. The PHA blend was composed of about 58-62% homo-polymer of3-hydroxybutanoic acid, and about 38-42% co-polymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 8-14% weight percent. The nucleating agent is cyanuricacid dispersed at a rate of 33% (by weight) in CITROFLEX® A4 plasticizerand milled.

This injection molding composition was compounded and then dry-blendedwith PBS. The PBS was BIONOLLE® 1001 (Showa Highpolymer Co., Ltd.,Japan). The formulations are shown in the table below.

TABLE 8 Compositions containing PHA blend and PBS 1 2 3 4 Formulation IMComposition (wt %) 100 90 80 50 PBS (wt %) 0 10 20 50 Total 100 100 100100 Data: Tensile Strength (Mpa) 27.1 26.5 27.4 33.0 Tensile Modulus(Mpa) 2915 2249 1959 1322 Tensile Elongation (%) 5.4 5.6 7.6 19.9Flexural Strength (Mpa) 36.1 41.6 39.8 36.1 Flexural Modulus (Mpa) 27482197 1879 1306 Notched Izod Impact 0.577 0.601 0.729 0.989 Strength(ft-lb/in) Onset Crystallization 118.29 114.22 115.16 111.21 Temperature(° C.) Peak Crystallization 113.82 110.19 111.21 106.33 Temperature (°C.)

As shown above, the addition of PBS caused a decrease in the flexuraland tensile modulus, but caused an increase in tensile strength, tensileelongation, and notched impact strength. The peak crystallizationtemperature was also decreased.

Addition of PBS also appeared to decrease the level of flash seen ininjection molded test bars, as shown in FIG. 9.

Example 9 Extruded Films Containing PBS or PBSA

In this example, extruded films were made and tested forbiodegradability. The following PHA formulation was made.

TABLE 9 PHA Formulation for Extruded Film Ingredient Wt % PHA Blend78.00 Nucleating Masterbatch 3.00 Calcium Carbonate 5.00 Slip AntiblockMasterbatch 5.00 CITROFLEX ® A4 plasticizer 8.73 Peroxide 0.18 PE3A 0.09

The PHA blend was composed of about 10-14% homo-polymer of3-hydroxybutanoic acid, and about 46-50% co-polymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 8-14 weight percent, and about 38-42% co-polymer of3-hydroxybutanoic acid and 4-hydroxybutanoic acid with the4-hydroxybutanoic acid composition being nominally 25-33 weight percent.The nucleating masterbatch was cyanuric acid that had been previouslycompounded at a rate of 33% (by weight) into a base resin of3-hydroxybutanoic acid and 4-hydroxybutanoic acid, and pelleted. Theslip anti-block masterbatch was a mixture of erucamide (20% by weight)diatomaceous earth (15% by weight) nucleant masterbatch (3% by weight),pelleted into PHA (62% by weight). The peroxide wastert-butylperoxy-2-ethylhexylcarbonate (available from Akzo Nobel asTRIGANOX® 117). PE3A was pentaerythritol triacrylate.

The formulation was compounded into pellets, which were then used tomake cast film using a ¾ inch RandCastle extruder.

Monolayer film was made from the above formulation. Monolayer PBSA filmwas also made. Coextruded film was also made, of composition PBSA/PHAFormulation/PBSA.

The same PHA formulation was combined with various antimicrobial agentsto produce monolayer extruded films, as described above. PolySept® Z(available from PolyChem Alloy) is a organic salt based, non-migratoryantimicrobial. “UDA” is Urtica dioica agglutinin. AgION is a silvercompound. AMICAL® 48 is diiodomethyl p-tolyl sulfone.

Biodegradability of the films was tested by soil burial for three weeks.The results are shown in the table and the graph below.

TABLE 10 Weight Loss of Extruded Films Buried in Soil Week 2 Week 3thick- weight thick- weight Film ness loss ness loss No. (mm) (g) (mm)(g) 1 PHA Blend monolayer film 0.276 0.007 0.284 0.063 (10 mil) 2 PBSA(2 mil) 0.064 0.004 0.060 0.008 3 PBSA/PHA/PBSA 0.100 0.007 0.102 0.018(35 take up) 4 PBSA/PHA/PBSA 0.096 0.007 0.106 0.014 (70 take up) 5 PHABlend monolayer film + 0.190 0.004 0.193 0.011 0.5% PolySept ® Z 6 PHABlend monolayer film + 0.245 0.002 0.240 0.002 1.0% PolySept ® Z 7 PHABlend monolayer film + 0.239 0.008 0.233 0.034 1.0% UDA 8 PHA Blendmonolayer film + 0.233 0.009 0.235 0.032 2.5% UDA 9 PHA Blend monolayerfilm + 0.245 0.014 0.234 0.044 0.5% AgION 10 PHA Blend monolayer film +0.229 0.004 0.252 0.028 2.0% AgION 11 PHA Blend monolayer film + 0.2050.007 0.191 0.013 0.1% AMICAL ® 48 12 PHA Blend monolayer film + 0.2160.008 0.229 0.009 0.8% AMICAL ® 48

The PBSA monolayer film degraded more slowly than the monolayer filmmade from the PHA blend.

As shown above, the PHA blend with added antimicrobial agents such asAMICAL® 48 and PolySept® Z degraded more slowly than the equivalent PHAblend film made without antimicrobial agents included. It degraded atapproximately the same rate as PBSA film.

Example 10 Blown Films Containing PBS or PBSA

In this example, blown films were made and tested for biodegradability.The following PHA formulation was made.

TABLE 11 PHA Formulation for Blown Film Ingredient Wt % PHA Blend 78.00Nucleating Masterbatch 3.00 Calcium Carbonate 5.00 Slip AntiblockMasterbatch 5.00 CITROFLEX ® A4 8.73 Peroxide 0.18 PE3A 0.09

The PHA blend was composed of about 34-38% homo-polymer of3-hydroxybutanoic acid, and about 22-26% co-polymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 8-14 weight percent, and about 38-42% co-polymer of3-hydroxybutanoic acid and 4-hydroxybutanoic acid with the4-hydroxybutanoic acid composition being nominally 25-33 weight percent.The nucleating masterbatch was cyanuric acid that had been previouslycompounded at a rate of 33% (by weight) into a base resin of3-hydroxybutanoic acid and 4-hydroxybutanoic acid, and pelleted. Theslip anti-block masterbatch was a mixture of erucamide (20% by weight)diatomaceous earth (15% by weight) nucleant masterbatch (3% by weight),pelleted into PHA (62% by weight). The peroxide wastert-butylperoxy-2-ethylhexylcarbonate (available from Akzo Nobel asTRIGANOX® 117). PE3A was pentaerythritol triacrylate.

This PHA formulation was then combined with PBS or PBSA, in ratios of90/10 (formulations 2 and 5), 75/25 (formulations 3 and 6), and 60/40(formulations 4 and 7) ratios of PHA blend and PBS or PBSA, as shown.

TABLE 12 Formulations for Blown Film Ingredient 1 2 3 4 5 6 7 8 PHA78.00 70.2 58.5 46.8 70.2 58.5 46.8 58.5 Formulation PBS —  7.8 19.531.2 — — — — PBSA — — — —  7.8 19.5 31.2 —

Blown films were made from these formulations, and tested by soilburial. The results are shown in the table and the graph below.

TABLE 13 Weight Loss of Blown Films Made with Antimicrobial Agents Week2 Week 3 thick- weight thick- weight Film ness loss ness loss No. (mm)(g) (mm) (g) 1 PHA Blend monolayer film 0.058 0.007 0.063 0.018 2 PHABlend/PBS monolayer 0.070 0.009 0.039 0.010 film (90/10) 3 PHA Blend/PBSmonolayer 0.062 0.006 0.057 0.015 film (75/25) 4 PHA Blend/PBS monolayer0.046 0.007 0.068 0.013 film (60/40) 5 PHA Blend/PBSA 0.045 0.011 0.0710.018 monolayer film (90/10) 6 PHA Blend/PBSA 0.059 0.007 0.057 0.011monolayer film (75/25) 7 PHA Blend/PBSA 0.065 0.008 0.049 0.012monolayer film (60/40) Films 2-7 showed a slower rate of weight lossrelative to the control (film no. 1).

Example 11 Compositions Containing PHBV and PBSA with Organic Peroxide

In several previous examples, it was shown that when PHA/PBS andPHA/PBSA formulations are prepared by melt-blending in the presence of areactive compound such as an organic peroxide, some synergisticrheological observations are evident. These formulations, created in areactive environment, displayed considerably higher melt strength andbetter melt stability compared to formulations created without peroxide;the PHA phase also crystallized at a higher temperature in theseformulations.

The present example shows data for a PHBV (7% HV) melt-compounded withPBSA in the presence of an organic peroxide. The relative proportions ofthe PHBV and PBSA phases were varied while all other additives(plasticizer) were kept unchanged. Formulations 1-4 were made withoutperoxide while Formulations 5-8 included 0.2% by wt. peroxide. Thecompositions are described in Table 14 below along with the meltviscosity, melt strength and melt stability data. All formulations werecompounded using a 27 mm MAXX Leistritz co-rotating twin-screw extruderwith the ten barrels and die zones set at175/175/170/170/170/165/165/165/160/160(° C.).

TABLE 14 Compositions containing PHBV and PBSA reactively blended withperoxide. 1 2 3 4 5 6 7 8 Component (Wt %) PHBV* 95 85 75 65 95 85 75 65PBSA BIONOLLE ® 0 10 20 30 0 10 20 30 3001 CITROFLEX ®A4 5 5 5 5 4.8 4.84.8 4.8 Peroxide 0 0 0 0 0.2 0.2 0.2 0.2 Total (Wt %) 100 100 100 100100 100 100 100 Torsional Melt Rheology G′ @ 0.25 rad/s (Pa) 3 3 17 4768 22 616 757 Eta* @ 0.25 rad/s 520 521 759 1088 904 798 4182 4418 (Pa ·s) Capillary Melt Rheology Eta @ 5 min (Pa · s) 341 339 359 373 330 375414 532 Capillary Melt −0.13 −0.11 −0.10 −0.10 −0.12 −0.12 −0.09 0.08Stability *PHBV in the above table was previously compounded withnucleating agent and plasticizer

The PBSA blended with PHBV was BIONOLLE® 3001 (Showa Highpolymer Co.,Ltd., Japan). The peroxide used in this example was TRIGONOX® 131(tert-amylperoxy 2-ethylhexyl carbonate) from Akzo Nobel. The data inTable 14 shows that with the addition of PBSA, the melt strength wasimproved by a factor of 16 compared to the PHBV composite. Marginalimprovements with PBSA addition were also observed for the meltstability and viscosity. However with the addition of the peroxide, themelt strength improved by a factor of 250 for the highest level of PBSAadded. The melt stability also improved by 39% while the meltviscosities were also shown to improve.

Example 12 Compositions Containing PHA, PBS, Organic Peroxide andCo-Agent

In this example, rheological data for a PIMA reactively melt-compoundedwith PBS in the presence of an organic peroxide and co-agent ispresented. The proportions of the PHA and PBS phases as well as theadditive were kept constant while the concentrations of peroxide andco-agent were varied. Other additives included in the formulations wereSUPERCOAT™ calcium carbonate (Imerys Performance Minerals), aPlasticizer Masterbatch which was a 50/50 mixture of the plasticizersCITROFLEX® A4 (Vertellus Specialties Inc.) and PARAPLEX™ 8600(Hallstar); a Slip/antiblock Master Batch which was a mixture composedof 15% by wt. Erucamide (Croda), 15% by wt. OPTIBLOC™ 10 talc filler(Specialty Minerals), a nucleating agent master batch Nuc. MB #1 whichwas composed of cyanuric acid compounded at 33% by wt. into a base PHAresin of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid and 68% bywt. PHA copolymer blend composed of about 34-38% homo-polymer of3-hydroxybutanoic acid, and about 22-26% co-polymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 10-12 weight percent, and about 38-42% co-polymer of3-hydroxybutanoic acid and 4-hydroxybutanoic acid with the4-hydroxybutanoic acid composition being nominally 30 weight percent;peroxide branching agent (Akzo Nobel) #1—TRIGONOX® 101(2,5-di(tert-butylperoxy)hexane) and #2—TRIGONOX® 131 (tert-amylperoxy2-ethylhexyl carbonate); co-agent SR231 diethyleneglycol dimethacrylate(Sartomer). The PBS was BIONOLLE® 1001 (Showa Highpolymer Co., Ltd.,Japan). The PHA was a blend composed of about 34-38% homo-polymer of3-hydroxybutanoic acid, and about 22-26% co-polymer of 3-hydroxybutanoicacid and 4-hydroxybutanoic acid, where the 4-hydroxybutanoic acid isapproximately 8-14 weight percent, and about 38-42% co-polymer of3-hydroxybutanoic acid and 4-hydroxybutanoic acid with the4-hydroxybutanoic acid composition being nominally 25-33 weight percent.The compositions are described in Table 15 below along with the meltviscosity and melt strength data.

All formulations were compounded using a 26 mm Coperion co-rotating,twin-screw extruder using the following temperatures (from feed to die)100/175 to 180/190/150/139/141/138/140/152/158 to 160/174/220(° C.),screw speed was 350 rpm and die pressure 1730 psi.

TABLE 15 Compositions containing PHA and PBS reactively blended withperoxide and co-agent. 1 2 3 4 Component (Wt %) PHA 45 45 45 45 PBSBIONOLLE ® 1001 30 30 30 30 CaCO₃ 10 10 10 10 Nuc. MB #1 3 3 3 3Slip/antiblock MB 4 4 4 4 Plasticizer MB 7.87 7.92 7.93 7.95 Peroxide #10 0 0.04 0.03 Peroxide #2 0.08 0.05 0 0 Co-agent SR231 0.05 0.03 0.030.02 Total (Wt %) 100 100 100 100 Torsional Melt Rheology G′ @ 0.25rad/s (Pa) 2383 1216 1651 1945 Eta* @ 0.25 rad/s (Pa · s) 14620 971013380 14390The data in Table 15 shows that the type and amount of peroxide andco-agent used to reactively blend the PBS with PHA can have an effect onthe rheological properties of the final mixture. Therefore the type andamount of peroxide/co-agent in the formulation needs to be optimizedtogether in order to maximize the melt properties for each blend.

Unless otherwise expressly specified, all of the numerical ranges,amounts, values and percentages, such as those for amounts of materials,elemental contents, times and temperatures of reaction, ratios ofamounts, and others, in the following portion of the specification andattached claims may be read as if prefaced by the word “about” eventhough the term “about” may not expressly appear with the value, amount,or range. Accordingly, unless indicated to the contrary, the numericalparameters set forth in the following specification and attached claimsare approximations that may vary depending upon the desired propertiessought to be obtained by the present invention. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains errornecessarily resulting from the standard deviation found in itsunderlying respective testing measurements. Furthermore, when numericalranges are set forth herein, these ranges are inclusive of the recitedrange end points (i.e., end points may be used). When percentages byweight are used herein, the numerical values reported are relative tothe total weight.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges subsumed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of 1 and the recited maximum valueof 10, that is, having a minimum value equal to or greater than 1 and amaximum value of equal to or less than 10. The terms “one,” “a,” or “an”as used herein are intended to include “at least one” or “one or more,”unless otherwise indicated.

Any patent, publication, or other disclosure material, in whole or inpart, that is said to be incorporated by reference herein isincorporated herein only to the extent that the incorporated materialdoes not conflict with existing definitions, statements, or otherdisclosure material set forth in this disclosure. As such, and to theextent necessary, the disclosure as explicitly set forth hereinsupersedes any conflicting material incorporated herein by reference.Any material, or portion thereof, that is said to be incorporated byreference herein, but which conflicts with existing definitions,statements, or other disclosure material set forth herein will only beincorporated to the extent that no conflict arises between thatincorporated material and the existing disclosure material.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein is used in the practiceor testing of the present invention, suitable methods and materials aredescribed below. All publications, patent applications, patents, andother references mentioned herein are incorporated by reference in theirentirety. In case of conflict, the present specification, includingdefinitions, will control. In addition, the materials, methods, andexamples are illustrative only and not intended to be limiting.

All of the features disclosed in this specification may be combined inany combination. Each feature disclosed in this specification may bereplaced by an alternative feature serving the same, equivalent, orsimilar purpose. Thus, unless expressly stated otherwise, each featuredisclosed is only an example of a generic series of equivalent orsimilar features.

From the above description, one skilled in the art can easily ascertainthe essential characteristics of the present invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions. Thus, other embodiments are also within the scope of thefollowing claims.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

What is claimed is:
 1. A method of preparing a branched polymercomposition, comprising reacting a PHA comprising apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer and PBS, PBSA orcombinations with a branching agent, thereby forming a branched polymercomposition of PHA and PBS, a branched polymer of PHA and PBSA or abranched polymer Of PHA, PBS, and PBSA; wherein the branching agent isselected from: dicumyl peroxide, t-amyl-2-ethylhexyl peroxycarbonate,1,1-bis (t-butylperoxy)-3,3,5-trimethylcyclohexane,2,5-dimethyl-2,5-di(t-butylperoxy)hexane,2,5-bis(t-butylperoxy)-2,5-dimethylhexane,2,5-dimethyl-2,5-di(t-butylperoxy)hexane-3, di-t-butyl peroxide, benzoylperoxide, di-t-amyl peroxide, t-butyl cumyl peroxide, n-butyl-4,4-bis(t-butylperoxy)valerate,1,1-di(t-butylperoxy)-3,3,5-trimethyl-cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-amylperoxy)-cyclohexane,2,2-di(t-butylperoxy)butane, ethyl-3,3-di(t-butylperoxy)butyrate,2,2-di(t-amylperoxy)propane, ethyl-3,3-di(t-amylperoxy)butyrate,t-butylperoxy-acetate, t-amylperoxyacetate, t-butylperoxybenzoate,t-amylperoxybenzoate, and di-t-butyldiperoxyphthalate.
 2. The method ofclaim 1, wherein the composition further comprises one or moreadditives.
 3. The method of any one of claim 1, wherein the compositionfurther comprises a cross-linking agent for reacting with the polymercomposition.
 4. The method of claim 3, wherein the cross-linking agentis diallyl phthalate, pentaerythritol tetraacrylate, trimethylolpropanetriacrylate, pentaerythritol triacrylate, dipentaerythritolpentaacrylate, dietliylene glycol dimethacrylate, bis(2-methacryloxyethyl) phosphate, or combinations thereof.
 5. The methodof claim 3, wherein the cross-linking agent is an epoxy-functionalstyrene-acrylic polymer, an epoxy-functional acrylic copolymer, anepoxy-functional polyolefin copolymer, an oligomer comprising a glycidylgroup with an epoxy functional side chain, an epoxy-functionalpoly(ethylene-glycidyl methacrylate-co -methacrylate), or an epoxidizedoil or combinations thereof.
 6. The method of claim 1, furthercomprising a nucleating agent.
 7. The method of claim 1, wherein theamount of PHA in the polymer composition is 5% to 95% by weight of thecomposition; is 20%-60% by weight of the composition; or is 30%-50% byweight of the composition.
 8. A method of making an article comprising abranched polymer composition of a PHA and PBS, comprising the steps of:melt-blending a PHA and PBS and a branching agent under conditions thatcause melting and branching of the PHA polymer and the PBS, therebyforming a molten branched polymer composition of PBS and PHA; andforming an article from the branched molten polymer composition; therebymaking an article comprising branched polymer composition of branchedPHA and branched PBS; wherein the branching agent is selected from:dicumyl peroxide, t-amyl-2-ethylhexyl peroxycarbonate,1,1-bis(t-butylperoxy)-3,3,5-trimethycyclohexane,2,5-dimethyl-2,5-di(t-butylperoxy) hexane,2,5-bis(t-butylperoxy)-2,5-dimethylhexane,2,5-dimethyl-2,5-di(t-butylperoxy)hexane-3, di-t-butyl peroxide, benzoylperoxide, di-t-amyl peroxide, t-butyl cumyl peroxide,n-butyl-4,4-bis(t-butylperoxy)valerate,1,1-di(t-butylperoxy)-3,3,5-trimethyl-cyclohexane,1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-amylperoxy)-cyclohexane,2,2-di(t-butylperoxy)butane, ethyl-3,3-di(t-butylperoxy)butyrate,2,2-di(t-amylperoxy)propane, ethyl-3,3-di(t-amylperoxy)butyrate,t-butylperoxy-acetate, t-amylperoxyacetate, t-butylperoxybenzoate,t-amylperoxybenzoate, and di-t-butyldiperoxyphthalate.
 9. A method ofmaking an article comprising a branched polymer composition of a PHA andPBSA, melt-blending a PHA and PBSA and a branching agent underconditions that cause melting and branching of the PHA polymer and thePBSA, thereby forming a molten branched polymer composition; and formingan article from the branched molten polymer composition; thereby makingan article comprising branched polymer composition of branched PHA andbranched PBSA; wherein the branching agent is selected from: dicumylperoxide t-amyl-2-ethylhexyl peroxycarbonate,1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane,2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-bis(t-butylperoxy)-2,5-dimethylhexane,2,5-dimethyl-di(t-butylperoxy)hexyne-3, di-t-butyl peroxide, benzoylperoxide, di-t-amyl peroxide, t-butyl cumyl peroxide, n-butyl-4,4-bis(t-butylperoxy)valerate,1,1-di(t-butylperoxy)-3,3,5-trimethyl-cyclohexane, 1,1-di(t-butylperoxy)cyclohexane, 1,1-di(t-amylperoxy)-cyclohexane,2,2-di(t-butylperoxy)butane, ethyl-3,3-di(t-butylperoxy)butyrate,2,2-di(t-amylperoxy)propane, ethyl-3,3-di(t-amylperoxy)butyrate,t-butylperoxy-acetate, t-amylperoxyacetate, t-butylperoxybenzoate,t-amylperoxybenzoate, and di-t-butyldiperoxyphthalate.
 10. The method ofclaim 8, wherein the article is a film and the film has 25% greater tearresistance according to ASTM D1922-06, 25% greater tear punctureresistance according to D1709-04, or 25% greater tear tensile strengthaccording to D882-02 than a corresponding polymer film consisting of PHApolymer.
 11. The method of claim 8, wherein the article is an injectionmolded article having increased tensile strength as measured ASTMD638-03, relative to a corresponding injection molded article consistingof PHA polymer, having increased impact strength as measured by ASTMD256-06, relative to a corresponding injection molded article consistingof PHA polymer, or biodegrades more slowly than a corresponding PHAinjection molded article consisting of PHA polymer.
 12. The method ofclaim 1, wherein the polyhydroxyalkanoate polymer further comprises apoly(3-hydroxybutyrate) homopolymer, apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with 5% to 15%4-hydroxybutyrate content, apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) with 5% to 22%3-hydroxyvalerate content, apoly(3-hydroxybutyrate-co-5-hydroxyvalerate) with 5% to 15%5-hydroxyvalerate content, or apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with 3% to 15%3-hydroxyhexanoate content.
 13. The method of claim 1, wherein thepolyhydroxyalkanoate polymer further comprises a) apoly(3-hydroxybutyrate) homopolymer blended with b) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate); a) apoly(3-hydroxybutyrate) homopolymer blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate); a) apoly(3-hydroxybutyrate) homopolymer blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate); a) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate); a) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) or a) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate).
 14. The method of claim1, wherein the polyhydroxyalkanoate polymer further comprises a) apoly(3-hydroxybutyrate) homopolymer blended with b) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15%4-hydroxybutyrate content; a) a poly(3-hydroxybutyrate) homopolymerblended with b) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5%to 22% 3-hydroxyvalerate content; a) a poly(3-hydroxybutyrate)homopolymer blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15%3-hydroxyhexanoate content; a) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15%4-hydroxybutyrate content blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22%3-hydroxyvalerate content; a) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with 5% to 15%4-hydroxybutyrate content blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15%3-hydroxyhexanoate content or a) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22%3-hydroxyvalerate content blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15%3-hydroxyhexanoate content.
 15. The method of claim 13, wherein thebiologically-produced polyhydroxyalkanoate further comprises a) apoly(3-hydroxybutyrate) homopolymer blended with b) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) and the weight of polymera) is 5% to 95% of the combined weight of polymer a) and polymer b); a)a poly(3-hydroxybutyrate) homopolymer blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) and the weight of polymera) is 5% to 95% of the combined weight of polymer a) and polymer b); a)a poly(3-hydroxybutyrate) homopolymer blended to with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and the weight of polymera) is 5% to 95% of the combined weight of polymer a) and polymer b); a)a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) and the weight of polymera) is 5% to 95% of the combined weight of polymer a) and polymer b); a)a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and the weight of polymera) is 5% to 95% of the combined weight of polymer a) and polymer b); ora) a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) and the weight of polymera) is 5% to 95% of the combined weight of polymer a) and polymer b). 16.The method of claim 13, wherein the weight of polymer a) is 20% to 60%of the combined weight of polymer a) and polymer b) and the weight ofpolymer b) is 40% to 80% of the combined weight of polymer a) andpolymer b).
 17. The method of claim 1, wherein the polyhydroxyalkanoatepolymer further comprises a) poly(3-hydroxybutyrate) homopolymer blendedwith b) a poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50%4-hydroxybutyrate content; a) a poly(3-hydroxybutyrate) homopolymerblended with b) a poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a20% to 50% 5-hydroxyvalerate content; a) a poly(3-hydroxybutyrate)homopolymer blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50%3-hydroxyhexanoate content; a)poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15%4-hydroxybutyrate content blended with b) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50%4-hydroxybutyrate content; a)poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15%4-hydroxybutyrate content blended with b) apoly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50%5-hydroxyvalerate content; a) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with 5% to 15%4-hydroxybutyrate content blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50%3-hydroxyhexanoate content; a) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22%3-hydroxyvalerate content blended with b)poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50%4-hydroxybutyrate content; a) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22%3-hydroxyvalerate content blended with b) apoly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50%5-hydroxyvalerate content; a) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22%3-hydroxyvalerate content blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50%3-hydroxyhexanoate content; a) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15%3-hydroxyhexanoate content blended with b) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50%4-hydroxybutyrate content; a) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15%3-hydroxyhexanoate content blended with b) apoly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50%5-hydroxyvalerate; or a) a poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)with a 3% to 15% 3-hydroxyhexanoate content blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50%3-hydroxyhexanoate content.
 18. The method of claim 1, wherein thebiologically-produced polyhydroxyalkanoate further comprises a) apoly(3-hydroxybutyrate) homopolymer blended with b) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50%4-hydroxybutyrate content and the weight of polymer a) is 5% to 95% ofthe combined weight of polymer a) and polymer b); a) apoly(3-hydroxybutyrate) homopolymer blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 20% to 50%5-hydroxyvalerate content and the weight of polymer a) is 5% to 95% ofthe combined weight of polymer a) and polymer b); a) apoly(3-hydroxybutyrate) homopolymer blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50%3-hydroxyhexanoate content and the weight of polymer a) is 5% to 95% ofthe combined weight of polymer a) and polymer b); a) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15%4-hydroxybutyrate content blended with b)poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50%4-hydroxybutyrate content and the weight of polymer a) is 5% to 95% ofthe combined weight of polymer a) and polymer b); a) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15%4-hydroxybutyrate content blended with b)poly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50%5-hydroxyvalerate and the weight of polymer a) is 5% to 95% of thecombined weight of polymer a) and polymer b); a) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 5% to 15%4-hydroxybutyrate content blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50%3-hydroxyhexanoate content and the weight of polymer a) is 5% to 95% ofthe combined weight of polymer a) and polymer b); a) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22%3-hydroxyvalerate content blended with b) poly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50% 4-hydroxybutyratecontent and the weight of polymer a) is 5% to 95% of the combined weightof polymer a) and polymer b); a) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22%3-hydroxyvalerate content blended with b) apoly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50%5-hydroxyvalerate and the weight of polymer a) is 5% to 95% of thecombined weight of polymer a) and polymer b); a) apoly(3-hydroxybutyrate-co-3-hydroxyvalerate) with a 5% to 22%3-hydroxyvalerate content blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50%3-hydroxyhexanoate content and the weight of polymer a) is 5% to 95% ofthe combined weight of polymer a) and polymer b); a) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15%3-hydroxyhexanoate content blended with b) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20-50%4-hydroxybutyrate content and the weight of polymer a) is 5% to 95% ofthe combined weight of polymer a) and polymer b); a) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15%3-hydroxyhexanoate content blended with b) apoly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50%5-hydroxyvalerate and the weight of polymer a) is 5% to 95% of thecombined weight of polymer a) and polymer b); or a) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3% to 15%3-hydroxyhexanoate content blended with b) apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) having a 5%-50%3-hydroxyhexanoate content and the weight of polymer a) is 5% to 95% ofthe combined weight of polymer a) and polymer b).
 19. The method ofclaim 17, wherein the weight of polymer a) is 20% to 60% of the combinedweight of polymer a) and polymer b) and the weight of polymer b is 40%to 80% of the combined weight of polymer a) and polymer b).
 20. Themethod of claim 17, wherein the biologically-producedpolyhydroxyalkanoate is further blended with polymer c) apoly(3-hydroxybutyrate-co-4-hydroxybutyrate) with a 20% to 50%4-hydroxybutyrate content; apoly(3-hydroxybutyrate-co-5-hydroxyvalerate) with a 20% to 50%5-hydroxyvalerate content or apoly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 5% to 50%3-hydroxyhexanoate content.
 21. The method of claim 20, wherein theweight of polymer c) is 5% to 95% of the combined polymer weight ofpolymer a), polymer b) and polymer c); or 5% to 40% of the combinedpolymer weight of polymer a), polymer b) and polymer c).
 22. Thecomposition made by the method of claim
 1. 23. An article made by themethod of claim
 1. 24. A composition comprising branched PHA andbranched PBS wherein the PHA is a PHA blend of about 58-62% homo-polymerof 3-hydroxybutanoic acid, and about 38-42% copolymer of3-hydroxybutanoic acid and 4-hydroxybutanoic acid, where the4-hydroxybutanoic acid is about 8-14% weight percent.
 25. Thecomposition of claim 24, wherein the PHA further comprises a copolymerof about 34-38% homo-polymer of 3-hydroxybutanoic acid, and about 22-26%co-polymer of 3-hydroxybutanoic acid and 4-hydroxybutanoic acid, wherethe 4-hydroxybutanoic acid is approximately 8-14 weight percent.